This will probably be a wildly unpopular thing to say, but there's a good chance that his ASD is playing a part in his behaviour. ASD can mean lack of insight, difficulty managing emotions, inability to instinctively know that some behaviours are wrong. Black and white thinking. Difficulty seeing the other person's perspective. Difficulty communicating.
From what you've said, I could see how ASD could exacerbate what's been going on.
But, also, here's the thing - it's possible to have ASD and still be a shitty person. It's possible that the ASD traits are amplifying the fact that's he's pretty unpleasant. Not everyone who has ASD is a saint whose immaculate behaviour is thwarted by their neurological difficulties. Some people with ASD are just fucking arseholes, and the ASD stuff is a convenient excuse to hang it on.
Waiting until you've got it all in your head to discuss it makes sense. I wonder whether it would be helpful for you to write it down in a form that you could give to him? This would give him the opportunity to go back over what you've said and take it in properly.
I also think you're in this trap of believing that what's going on isn't "bad enough". When there are good times, when you're not being beaten up or constantly facing nasty comments and put-downs, it's easy to think that because you "don't have it as bad" as some of the other horror stories you will have read, that you need to put up with it. That you're just being sensitive. That it's your fault for causing it.
If you aren't happy, that's "enough". You don't need any other reason to call time on the relationship. Doesn't matter if he is the most saintly man in the world - if you are not feeling happy and relaxed in your own home, then it's perfectly fine to say "I'm not feeling OK about this".
You haven't expressed any loving feelings towards him in this thread. Your concerns about splitting seem to be based on your children. I have two ASD children, twins. My son has a lot more difficulties and was diagnosed many years ago. My daughter was only diagnosed a few months ago - they're 10 yrs old so her difficulties are suddenly becoming more apparent. However, she has spent many years taking care of her brother - in nursery, schools etc - and making sacrifices. And that's heartbreaking to see. So I totally understand where you're coming from with all of that, and why you'd have such concerns about not just your DS but the impact on your DD. My son wouldn't cope away from me for a weekend and this would be a dealbreaker for me. But would your DH actually want them for the weekend? He can't manage to get your son in a bath, for example. How's he going to take care of them? Your DC are at an age now where their views would be taken into account for contact and visits (I believe). Maybe start including in your diary all the times that you've had to step in/carry out tasks for your DC as your DH wasn't able.
Another really controversial view: maybe you decide to stay until your DC are older. It's shit and you shouldn't have to consider this as an option, but if your DS and DD would be so affected by being without you and your DH would want overnight custody - maybe the answer is that you stay until they are 15/16 - which if I've understood correctly is only a couple of years away? That really depends on your mental health, and whether you feel able to stand up to him during that time and whether he will accept your refusal to have sex if you don't want it. Unfortunately I know a few SEN families where the relationship has broken down but due to the needs of the children, the parents are just hanging on until the children are older and don't need so much support before they split. It's a shit situation but having a child with additional needs sometimes means there's not much other choice. Equally, I know some SEN families where the parents have split and it's actually worked out totally fine. SEN puts an enormous toll on even the healthiest relationship and means you are in full-on carer mode for much longer than you anticipated.
I'm also going to say this loud and clear - you are not unreasonable or at fault in any way for refusing to have sex. Yes, there are threads here where women talk about feel hurt and rejected if their partner doesn't want sex. And your DH probably feels the same way. And that's a shame. But a decent partner will seek out solutions and communicate, not suggest some batshit crazy sex schedule three times a week. Your DH is free to leave you if he doesn't feel happy. We are each responsible for our own happiness - it's not up to you to engage in acts which you dread just to keep him feeling happy.
Personally OP, I think you should investigate how to leave him. Your children will be struggling in an atmosphere where he's moody and passive aggressive. You've probably noticed your DS getting anxious when your DH is slamming stuff around. You'll breathe easier. Life will be more relaxed for you all. You won't be scared to go to bed. You won't have to creep upstairs to pick stuff up without antagonising him. But I understand the custody of the DC is a concern. I wonder, would a free consultation with a solicitor help with this at all?
I hope you find a way forward. Sending love x
