You might get more advice.  Not everyone check individual blogs, nor comment.

It's like the difference between writing in your diary every day (blog) versus having a conversation with a group of individuals (forum posts).  

That being said, I think you and your wife are looking at parenting from different perspectives.  She wants you all-in with her kids but she does not feel the same with your son, correct?  Why is that?  Did you ever sit down with her when kids aren't around and ask her?

If she has three kids from three father's that is troubling in itself.   Plus, she has no financial support from any of them so they sound like a trio of losers.   You are paying support for your child, as you should, yet she resents it.  That is entirely unreasonable and ridiculous for her to resent that.

To be honest, it doesn't sound like you have a solid marriage.  Perhaps you may need to spend time living apart from each other to gain clarity on whether to stay married or not.  During the separation, you can focus on your son and she on her brood.

Ok, so I can only assume the child support you pay is court ordered? If so, it's not a choice. Even if it is not, why doesn't she think you should have to help support your own child? Do you have 50/50 custody?

Why isn't she getting child support? Do all 3 fathers have 50/50 custody? Please tell me she is very gainfully employed and you are not supporting her kids financially.

Do NOT allow your wife to treat you child horribly. Your #1 job as a parent is to protect your child. 

So you were all lovey dovey with your wife until your kids came along? Why can’t you balance your roles? Your kids were never in her life until now. She helped you get your kids back because she never even considered that your relationship with her would change. Sounds like she loved you enough to get your kids back. So what has changed? She doesn’t have a relationship with your kids and she is under no obligation to treat them like she is their mother.

And I hope this is not a real post. That is all I have to say.

Your partner shouldn't give you a hard time because you give your ex child support for your son, this is completely out of order - you are just being responsible.   You can't expect her to love your son but you can expect her to treat him with courtesy when he is around her.  You sound like a nice bloke, don't let this woman take advantage of this - stand up for yourself, and if necessary, call time on the relationship if it is no good any more. 

Sometimes, love is not enough.

When it comes to relationships, this woman has failed at least three times before you, so something is definitely lacking with her. If your W wants this relationship to last, she needs individual therapy and you both need couples counseling. The best predictor of future behavior is past behavior, so if your W hasn't done any work on herself, the odds are against you.

Hard to give advice on a very vague description such as this. 

When you say your kids can be "hard", what does that mean? Does that mean they are breaking the law, physically violent, mentally abusive, disrespectful, etc? Or more like normal kids that have their quirks, which is extra grating on a SP?

Also, she says you're paying for your ex's nights out. Well, are you? Is the only way you get to see your kids is if you pay BM and take them? I'm 100% for everyone needing to pay for their own kids, but if you have allowed your ex to use your money as a bargaining chip, especially to the point that you become the ex's lap dog and can't take care of your own financial obligations, then I see why your partner is upset.

Additionally, where are the 3 fathers to her kids? Why don't they pay support? Are they dead or dead beats? Has she alienated the kids from their father? What???

Also, as a general rule, all because one SP dives in head first to being a SP doesn't mean that their partner has to do the same. I also think it's much easier for men to be successful SPs because the expectation of what they do is minimized versus that of a SM. SFs can play catch and help with homework and treat Mom right and are seen as a gold standard. Women, however, are expected to act 100% motherly and cook, clean, transport, help with homework and bedtimes, form relationships with the ILs, etc and get a 50/50 shot at being told "well that's just what you do" or "you're overstepping and should back off so you don't upset BM, but don't back off *too* much because then the kids and the rest of society will KNOW you hate them".

I can see this situation several different ways. First, your SO may have picked a bad lot to procreate with and has raised her kids on her own, making them respectful of her home and those she brings into it (you). That allowed you to form good bonds with her kids because she told them to suck it up and be kind. Your kids, however, because you haven't seen them, haven't been raised the same (either because they don't respect you for not being around or thei r BM has poisoned them against you and yours). That means they are hellions to your SO, which is quite a different relationship between them and her. Additionally, if you're afraid to lose your kids again, you may allow them to be hellions or allow them to get away with weak apologies or you make excuses like "they're just kids" instead of demanding they respect your home and SO. You become a Disney Dad and guilt parent versus actually parenting and supporting your partner, which also causes strife between her and her kids bevause your kids get away with murder while hers are held to a different standard. Then, because of your fear of losing your children again, you are at BM's beck and call, so the visitation schedule is chaotic, and you are the one buying everything for the kids to make up for lost time, AND you're paying CS to a woman who doesn't spend it on the kids.

OR

Your SO expected you to step in and play Replacement Dad to her kids. She expected you to form bonds and then open up your pocketbook to her. When you went to see your kids, she didn't protest because she didn't think it would actually happen, but when it did, she realized her gravy train was about to run dry. Now she's just snippy that she didn't bag you fully and that "her resources" are being shared elsewhere with your actual responsibilities, your kids. I'm slightly less inclined to lean fully this way because, if her intention was to use you, she wouldn't have helped you with your kids.

The truth is likely somewhere in the middle. Your kids aren't angels, but you're not a strong parent with them so she is less inclined to form a relationship with them. She saw you as someone who would share in her parental responsibilities, including financially, but didn't fully think through having to be a SP herself. Your ex likely tries to manipulate money out of you and your SO sees it. However, it's pretty effed up to expect you not to pay when I'm sure she has felt the struggle of having 3 men not support their own kids.

The only way your marriage survives is if you all become REALLY honest with one another about your expectations and what is really going on. I think an outside view, a therapist, would work wonders. If you're not willing to do that, then pack your bags and leave because this won't get better until you're willing to look at and cleanse the festering wounds.