Good for you, Abby-- and you clearly have challenges most of us don't face. Three children in two years is a handful, notably with an autistic child.
Your horary chart, while not suggesting an ideal solution, does give you enormous strength as a domiciled, first house Saturn. The chart overall looks amazingly favourable, with all those trines and sextiles. The main issue being your husband. I think if you just explain to him your new regimen and stick to it, he should find something sufficiently paternal. For one thing, a 7-year old boy is no longer a tiny tot, and some easy sports activities, like kicking a soccer ball in the neighborhood park or back yard should be a good father-son activity
What would happen if you didn't:
1. make separate meals for everyone? Just one simple type of meal consistent with your son's diet. If your husband is unhappy with this arrangement, suggest he order take-out or fix his own food. He's the other parent, not the patriarch, and it is now 2019, not 1955.
You're under doctor's orders not to "suck it up" and overwork.
2. Sandwiches and oranges can be completely healthy. I did some "kids in the kitchen" activities with my 3-year old grandson last month, and he really enjoyed it. If you can lay out pre-sliced whole grain bread, meat, cheese, lettuce and tomatoes, or the occasional PB&J, the children could probably fix their own sandwiches. If you can score the orange peel with a sharp knife, the kids can peel their own oranges.
3. I once had a friend with a hyperactive ADD son, and a professional colleague with two autistic sons. Both moms found that cutting out sugar and food additives from their boys' diets helped. The colleague found that a gluten-free diet was helpful. Worth a try if you're not doing this already.
4. I recall my siblings and I fighting a lot as children, but in hindsight, I think it came from not getting enough active parental involvement. This is so hard to give when you are so stressed (as my mother probably was) but I think this is much more important than keeping a tidy house or making all those special meals.
5. The chore board is a great idea. One chore could be "help Mom with dinner"-- even if the help involves pushing the start button on the microwave. "Help Mum with laundry" could mean sorting their clothes into piles and pushing the start buttons on the washer and drier. 6 is still awfully young to shoulder major tasks, but if you start your daughters now, I think you'll find them growing into their roles in a year or two. Of course, small rewards for jobs well done are incentives. They could help decide what would be a small, meaningful reward for them.
Good luck, Mama-- and what can you do that is nice for yourself?