So what if SS10 is loyal to his mother?
So what if he gives a second by second account of what happens in your house?
That is not the  problem.
The problem is his mother using it as ammunition to fire back at you.
If you were dealing with a "normal" person, she would accept that unless you were endangering her child, she has no say over what happens in your house.
Even if she doesn't like it.

If she was a "normal person", capable of acting like an adult, she would look to engage you on things that are of concern to her.
May be she really wants to limit the amount of sugar the child consumes.
May be she really wants to cut the artificial ingredients in the child's diet.
Is the correct way to approach these concerns with you and DH firing off texts?
I dont think so.
These are obviously then not her concerns but her judgemental criticisms.

Also, do not overlook the possibility that it may NOT be SS volunteering information, but BM interrogating SS on what happened in your house.
Specifically so that BM has something to berate you and DH with.
If you are not doing anything alarming why do you take her texts to heart?
You are giving this woman space in your head.
You are allowing her to create trouble between you and DH.
You are playing into her sick game.
Please stop.

I know it is hard, but learn to grow a thick skin and an ability to ignore her meddling.
She is doing it to upset you or control you.
You are taking the bait.
Please don't.

You say you are confident in your parenting.
Believe it.
Act it.
In the end this is a YOU issue.
You need to take control of how you feel.
BM may not stop her meddling and nasty text messages.
If there are issues  of concern to engage her on, then maybe you and DH should talk to her about those issues.
If there isn't,  consider her  texts noise pollution.

This is something for you to take charge of.
Please do.

Expectations. You and DH need to have that talk. 

If you feel he is meeting and conforming to these demands of BM's despite your family and home life you need to tell him that. And come to an agreement that works for both of you. 

This exact thing did and still does happen with our HCBM. BUT, this is where we differ...

A. My SO handles all things HCBM. 

B. We have been very upfront with her that our home is our business. She is welcome to take her crazy issues to court, and lose, but we will not and never will entertain the accusations. 

C. I have absolutely no idea if and when she texts her crazy. Like I said SO handles all things HCBM. Unless it will impact me in a negative manner. 

D. We do not discuss anything of importance while skids could be within hearing distance. Most importantly my business and the business of my children are never a topic of conversation while skids are near. 

E. Both my SO and I are on the same page about all of the above. And we have declared our home a safe space. HCBM does not infiltrate and if she tries we shut it down immediately. That means SO addresses this often with skids. 

Our HCBM does interrogate skids each time they return. They also offer up info because they know she will reward them for it. Which means they often times will spy and scheme for info. But they have very little power here. That is where your issue is right now. We do as we choose as the adults. If skids do not like it they can go, and that has been said. If HCBM does not like it then, like I said, she can go cry to the judge!

Unless your husband is reacting to all these emails 'grading' his parenting and time with his son, there shouldn't be a problem. 

She's pulling the 'I am the Mommy and I know best' card. But it doesn't mean he has to pay any attention to her weekend review. She is obviously interrogating the kid upon his arrival back to her home. 

Unless there is truly something wrong going on at your home, who cares what BM thinks about how Dad/you run your household? Has the kid returned to BM with severe sunburn? Is there a section in the CO/PP that states 'Father must highly entertain child to child's and Mother's satisfaction on every visit?  Is the kid on a physician ordered strict diet that isn't being followed? 

I bet not to these items. So what's the problem? She and your DH made the decision to divorce and live separate lives and households. She's not Dad and his home isn't hers. He's not Mom and her home isn't his. They parent differently and have different rules and ideas/guidelines in their individual homes. Pretty common from home to home all across the US. 

Does she believe she is building documentation for a 'case' to remove parenting time from Dad? If this is all she can come up with, nothing to worry about. 

Relax. No need for the egg shell walk. She gave up 100% control when she and Dad divorced. She may not like the fact she did, but she did. However if Dad, is reacting and responding to all her busybody interfering or actually trying to jump and please her by doing everything in the manner she demands, well yes, then there is a problem. 

Share clothing with another set of kids? Seriously? LOL. Give her the name of the place you shop and she go go get her son some of the every same clothing. 

Don't respond to the emails or texts about stupid stuff like this. She is trying to have a foothold in your house as far as control goes. Cut her out of it as much as humanly possible. 

There is a fine line between explaining to a child the difference between "hiding or keeping" things from their mother and the general expectation that what goes on in one house on a day to day basis does not need to be repeated to the other household.

You don't want to give the kid the impression you are trying to hide things from the mother... but that how you parent and how your household runs is not up for discussion with his mother... and that while you aren't keeping secrets, it quite frankly isn't her business unless the issue is related to the safety of the child.  So, mommy doesn't have to know every item of food you put into your mouth or what you wore every day... she doesn't need to be privy to our private conversations... general responses are fine, she doesn't need a play by play.  We went for pizza after we went to the park.  vs we went to sal's pizza and I had orange soda with a pepperoni pizza and cookies.  We then went to the park and played tag and got some snicker's bars. etc...

Tell your DH to rename her “Ignore the whore” in his phone as a reminder to do just that. 

I agree with what other have said here, block her texts during visits. But... that kid should be taught that whilst it may be his loyalty to BM that is making him do this (and i'm sure he gets a lot of brownie points from her for doing this) he is being disloyal to his father. 

He is 10 so he should have the intelletual ability to understand that he is being unfair.

1)  Tell her to STFU, or ask her what kind of mental problem she has that necessitates her micromanaging your household.

2)  Start micromanaging every little thing SS does, report to others his underwear size and how often he poops and what the color and consistency is.  Ask him how it feels.

3)  Really give her something to bish about.  Start feeding SS ridiculous information, constantly.  Leave out brochures for speedboats you are buying.  Ask DH when the meth will be finished cooking.  Tell DH you are making liver for dinner.  Tell him next weekend you will all go bungee jumping.  Etc.  Have fun with it.

4)  Micromanage BM right back.  Send 10 texts a day with stuff SS supposedly said.  Heh.

5) Whatever she complains about, do it more, and remind SS to report it every time.  Have him tell her you are feeding him sugar.  Keep reminding him to tell her this or that, constantly.  The dog barked?  Tell her.  It's raining?  Tell her.  You're watching television?  Tell her.  SM has a booger in her nose?  "SS, tell BM!"