I know this is long but PLEASE HELP ME!

We started having problems with SS around March. He is six. We have him every weekend and Wednesdays from 5 to 7. In March he started calling DH and saying he didn't want to come over on Wednesdays. It wasn't every Wednesday, probably once a month. DH didn't want to force him to be here so if SS said he didn't want to come we wouldn't see him until Saturdays. He started acting out at school, not doing his school work, not listening to the teacher and not playing well with other kids. This was in kindergarten. After a particularly bad incident they sent him to the school psychologist and she spoke to BM and DH and told them she thought he needed therapy so he started seeing her once a week. Sometimes she would call DH or BM to come in to talk to them but for the most part it was just her and SS. We were supposed to start rewarding him for doing well in school to motivate him but it didn't work, he kept acting out and not doing his school work. Usually, SS's reward for doing well was sleeping over at MIL's on Saturday night or going on a bike tour on Sunday morning, but since he never did his work he never got to do these things. He would come home on the weekends with homework (coloring or cutting and pasting pictures, etc) and if he hadn't done his school work DH would have him finish whatever he didn't do at school. This was a big change for him because honestly we used to spend all weekend w my MIL or my niece who SS loves to play with. In June the therapist decided she wasn't really getting anywhere so she called us all in (BM w her husband, DH and myself and FIL) because she needed us all to be on the same page. She pretty much told us if SS misbehaved at school and his mother scolded him that DH could talk to him about it but shouldn't punish him because his mom had already scolded him, she said we should all be on the same page because SS's home life changed drastically from our house to BM's house. At our house he has his own room, he sometimes showered by himself (w minimal supervision), changed himself, DH did homework w him, etc. At BM's house he had his own bed but shared a room w BM and her husband. The therapist said even if they shared a room, he should be going to sleep by himself. At BM's he always showered w BM's husband and he or BM helped him get dressed. BM would sit him down to do his homework and check in on him every once in a while. The therapist told us we all needed to keep any problems to ourselves and not discuss them around SS. She said we needed to put boundaries, especially FIL because he would spoil SS terribly and take him wherever he wanted and do whatever he wanted whenever he wanted. He pretends to be sick whenever he isn't getting attention so she said we shouldn't give it to him unless we see that he is really sick. She told DH he had to call SS every night and she told BM she couldn't reject his calls. She got BM to agree to let DH pick up SS on extra days as long as SS was up for it. This started out well, but after about two weeks, SS stopped wanting to take DH's calls. DH would call BM and he could hear in the background that SS said he didn't want to talk to him. He would ask to come get him and SS would say he didn't want to come. We only ended up having him at most one extra afternoon a week. At this point, SS stopped going to see the therapist. He was supposed to continue to go during the summer one hour a week, but he went on vacation one week, then the therapist was out the next week and blah blah blah the point is he never went back. When school started back up, BM said that SS had a lot of homework and she wanted to go back to the original just Wednesday afternoon agreement. As they had never changed anything in writing, DH said OK. Since school started, SS hasn't called once to say he doesn't want to come for his Wednesday visit, but he still refuses to take DH's calls sometimes. Well this weekend BM asked to have SS back early on Sunday because her family was in from out of town and wanted to see SS. DH said no problem, we took him home at 1 PM on Sunday. Yesterday morning DH's boss told him he needed him to go out of town, so DH called BM and told her he wasn't going to be able to pick up SS for the Wednesday visit and asked to speak to SS to tell him. According to DH, this was the conversation:
DH: BM, I am going to have to go out of town for work and won't be able to pick up SS tonight. Can I speak to him?
BM: Ok. SS, you dad is on the phone.

In the background
SS: Which dad?
BM: Your father.
SS: "DH's first name"?
BM: Yes.
SS: I don't want to talk to him.

BM: He says he doesn't want to talk.
DH: Ok I will call him tomorrow.
BM: I wanted to talk about something...

According to DH, BM went on to tell him that SS had told her on Monday that he doesn't want to be w DH anymore. He comes here because he has to and sees it as an obligation. He doesn't think DH loves him and doesn't understand why he wasn't asked when they made custody agreement. He said DH punishes him too much and he doesn't have any fun over here.

SS is 6 now but was 4 when the custody agreement was made and ADORED DH. He wanted to be here ALL the time. BM had been telling DH that SS didn't want to talk to him for a while, but DH always believed BM was making it up because she is like that, but then he started hearing it for himself and so obviously now he believes her. For a long long time BM was crazy. She would use SS to get more money out of DH, if DH couldn't give her more money she would tell SS that DH didn't love him and that was why he wouldn't give him more money. SS is always telling us how his mom says that we are rich (I wish!) and she works so hard to pay for all his things because DH doesn't give him anything. Before the custody agreement DH paid BM CS and paid SS's tuition, clothes, etc. When they went to court, BM asked for more money. The judge gave it to her but told her that DH would no longer give her extra money for tuition or anything, only CS. For a while DH would give her extra when he could, but when we closed our store he told her he wouldn't be able to give her extra money and she called SS and said, "Your dad just told me he isn't going to pay for your school anymore, what do you think of that?" SS was about 4.5 at the time. When DH got a new job and started making more money, he offered to help BM w buying things for SS's birthday at school. He said he would get the cake or the party favors and she said, "No thanks, my husband has already bought SS everything he needs." Recently, DH, SS and I were walking past a store that sells uniforms for SS's school and he said we should stop in and get him some extra shirts to which SS replied, "Step dad has already bought me everything I need for school." SS is also REALLY attached to his step dad. The therapist said he didn't really see step dad as an authority and only really did what he said because BM made him, but I think he is really attached to him. He calls him dad and is always saying he wants to be like him. On Father's Day we took SS to compete in a bike race and BM showed up w her husband and her mother. SS saw them and ran to them and started yelling "Daddy." He jumped on him immediately and started kissing him and wouldn't let him go. He kept saying, "Dad come see my bike," and "Dad, look at my helmet." DH got very uncomfortable but didn't say anything, and when he got home later he asked SS not to call his step dad "Dad" in front of him.

I am sure I am making it seem very one sided and although I think BM did have a lot to do with SS's change of heart I am sure DH and I have made our share of mistakes. We try to play w SS when he is here, but it is very difficult. At BM's house SS has two cousins to play with, here it is just us and once in a while his cousin (but she recently started taking dance classes and music classes so isn't available when SS is with us.) We play with him as much as we can, but when we are doing dishes or cleaning up or doing work he says he is bored and we aren't any fun. DH has become more demanding w school, but honestly I don't think he is always punishing SS, maybe I just grew up with very strict parents, I don't know. If we go to MIL's house and SS asks to sleep over and DH says no because he didn't do his work, MIL and SIL will usually tell DH not to be so strict, to let him sleep over, they only see him once a week, he shouldn't punish SS, things like that. Well SS obviously sides w MIL and SIL and says DH is being mean and punishing him too much. I dunno, is this too much for a kid? He is only in 1st grade right now, maybe it is not that serious? Should DH just try to see SS when SS wants? Maybe do every other weekend so SS has fun time w BM as well? DH was really upset about all of this but I don't really know what to say. Before, SS would come and immediately want to see MIL or his cousin and DH would feel bad and tell me he felt like SS didn't want to be w him, but I always said, you know he is a kid, what kid doesn't want to see his grandmother whenever he can? But how do I respond to this? SS flat out saying he doesn't want to see DH? That it is an obligation? I know I am not the one who is going to end up making the decision, but DH did ask me what I thought we should do and I have nothing? Do we keep making him come and try to be more lenient? Do we give him space and let him come to us? Will that make SS feel like it is OK not to see his dad and that his dad doesn't care? I have also thought maybe it is me. I do care about SS but he is not my son and I do get annoyed with him much faster than DH. I never yell or punish him, and I try to play with him as much as I can and he likes to cook with me so we cook together. But sometimes I will go watch a movie by myself and leave them alone, or go get coffee with a girlfriend instead of going with them to MIL's house. SS usually asks to do homework with me because I am a teacher and he says I am more helpful than DH, but I know kids are intuitive and maybe he can feel that I get annoyed. Is it possible he feels like I don't want him here and that is why he doesn't want to come? I just don't know. If you made it to the end of this, thank you! and please help!