I so get your situation (wish I didn't!). I have three kids, two of them with some special needs (learning disabilities, neurodevelopmental disorder). Three dogs. Old high-upkeep house. I always wanted (and was clear about this!) a partnership that shared everything equally--financial responsibilities, child care, house and yard work, etc. I think it's possible to have an equal partnership when you have domains, but it comes with its own challenges, and more importantly, it's not what I wanted. I wanted us both working, both responsible for the kids, home, etc.
But DH has a job that requires travel, lots and lots of international travel (sometimes weeks on end). And no matter what I've done, or what I've said, or how hard I've tried to get him to understand how this impacts me and the kids, how much I've told him this isn't what we agreed to, it isn't what I want, it falls on deaf ears. (He claims to understand and promises he'll manage his travel, but we both know that's not possible in his line of work--he would need to find a different job and that never seems to happen).
So, I spent years and years seething with resentment and the injustice of it all (during 2/3s of our marriage, I was also outearning him substantially, so it felt really unfair, because I was doing more of EVERYTHING). DH is wonderful in so many ways, and he actually is really engaged in housework and childcare when he's home (but not at all when he's not). But I am always the "default" parent, and the one who has to manage everything, and keep track of everything, and step in and make sure everything gets done while he comes and goes, and quite frankly, it's exhausting. So a number of months ago, I decided to give up trying to change him (doh!) and do whatever I needed to do in order to make the rest of my life fit and do make sure the kids are thriving and that we're all happy.
Now, I wouldn't say I've succeeded in that, as I left my demanding job to take another demanding job, but I have gone down to 80% time and I'm clear that if this isn't working, it's on me to make further changes. And honestly, there is much less friction in our marriage as a consequence. At the end of the day, he contributes enough, even if it's not in the ways I thought he would. The way I look at it, his high-paying demanding job and his insistence on keeping it frees me up to make whatever decisions I need to to make things work for our family (and he is supportive of this).
So...for you, I like the idea of a one-year trial (my next move to reduce stress is to try to arrange a lower-level and even more part-time position, and barring that, leave my job for a one-year "sabbatical," which wouldn't technically be a sabbatical because it would require my quitting my job with no expectation of being rehired). But I'm not ready to make a decision to permanently leave the workforce and have SAHM be my new primary identity, though that very well could end up happening--I just feel like I would need to keep a foot in both worlds for awhile (psychologically) in order to gain comfort that I could handle being a SAHM and that it wouldn't change the dynamics in our marriage in a negative way.
I would also be clear with your DH that you are pausing your career in order take on the job of ensuring your DS's special needs are attended to, and I would retain the right to hire a housekeeper, part-time child care, etc. If you resent being responsible for all the household stuff, 24/7, one option is to get DH to step up (which doesn't really seem like an option) and another option is for you to oursource some of it until things feel balanced to you. There are things more important than RE and keeping marriages intact and meeting our kids' needs are two of those things.
Good luck with this--this is hard stuff and you're not the only one going through this.