Has he any inkling how bad the relationship has become?
When you said how his adhd serves him well in his work, it made me wonder if he thinks it’s serving him well at home too?
I actually think that one of your early suggestions to leave something about rsd in his path in the hopes of triggering a hyper focus is a good suggestion. If it works.
And I’m also going to suggest, because communication with him is so challenging, that if you bring this up with him, it might be best to hit hard and fast with the very scary truth of how dangerously close he is to destroying the relationship. If he’s going to shut down criticism, make your first sentence count. So that even if it hurts, he has a chance to hear what he really needs to know.
There are other ways to communicate besides words - and you’re already doing some of these but I’m guessing that your withdrawals probably haven’t registered. (My dps had communication issues - a bit different to yours - but my probably asd df didn’t register my dm’s passive aggressive withdrawals of affection )
It’s going to sound nasty to say that you should do something that affects him adversely. But I don’t mean you should be abusive (walk away before you ever get to that point) but as an example my dm would sleep on the sofa rather than share a bed with my df to make her point. He was oblivious - he enjoyed the extra space and assumed that she had moved to the sofa for space too, and he was happy for her. But if she locked the bedroom door and told him to sleep on the sofa he realised there was a problem.
This is clumsy to communicate. But my impression of you is that you don’t want to end your marriage, and that you have some compassion for his disability (even if it’s nearly exhausted). If he isn’t actually aware how much damage he is doing, then maybe he deserves a chance to try and fix it?
My point is to be conscious whether you’re protecting yourself, or hurting yourself - and I think it’s tipping into the latter for you at this point. I doubt he feels your withdrawal or silence. Packing his bag and telling him to go to his mother’s might get the point across because it inconveniences him directly. (As an example) Obviously passive aggressive communication is not the way forward. Finding a way to directly communicate is what’s ultimately needed (you may both need to develop better non verbal cues as well)
You’re a part of the problem (sorry) if you can’t find a way past the avoidance and people pleasing, because you are letting the relationship whither past recovery. And if you’re going to do that, would it not be better to just leave now (which is also a valid option)? Why waste more precious years? You deserve as much compassion as he does.
BUT - you are the best judge of your own situation - it may not be safe to do anything like this. Sometimes our instincts are protecting us from danger we haven’t openly acknowledged. If there’s a risk of harm, then your safety is paramount.
I’m not intending to be unkind here - or blaming you. But sometimes we get so focused on the other person’s problems that we lose sight of ourselves. Or we don’t recognise that we’re in danger.
The way we conceptualise abuse in marriage is a problem because a lot of women don’t recognise themselves as victims or their partner’s behaviour as abuse. Their perspective is that they are strong women with troubled men. And they don’t notice the erosion of their personhood because they are centering their partner’s problems before their own welfare. And social conditioning already demands that of women so when you’re in a difficult marriage the lines are blurred.
Have you any RL sources of help or support in tackling any of this? If you can find a counsellor with experience of neurodivergence (but whose neurotype matches your own) it might help to work through this. This is far too hard to manage all by yourself. But note that I’m not suggesting marriage counselling - that might be useful at some point (or not) but first find someone just for you. You’re putting a huge amount of thought into him/his problems/his conditions/his diagnosis. Counselling could give you a safe space, with a trained listener where you can use your voice fully without restraint.