Try to remember that he has dealt with health issues his whole life and now that he is on a health journey and feeling better, he probably thinks it’s the best thing on the planet because he finally feels better. If your kids have any allergies just know he is probably traumatized from his health issues and just doesn’t want his kids to go through the same thing. Have you tried to eat healthier with him? Maybe have 2 days a week where everyone eats healthy days? But he definitely needs to put his trauma aside and have his kids have a life too. Sorry you have to deal with this. I would say he needs to compromise
Reframing foods from "good" and "bad" to "on" or "not on" his diet will help the whole family. Remember he's trying to push this on you guys because he feels regret and shame over his past choices and is trying to save you from those feelings because he loves you. That doesn't mean you have to live in a bubble or your kids can't have French fries occasionally. Have general rules you can agree on for the kids' food so you don't have to hear about every nugget. Kids have different nutritional needs than he does, and there are plenty of resources that show what a balanced plate might look like. You can probably get one from their pediatrician. If he brings it up when you're preparing food, you can gently remind him that's HIS meal plan, not yours or theirs. For the cloud ceiling, is he just suggesting you can't clean it at all? That you wouldn't notice your children's allergies and know it's time to clean it or take it down? He needs to apologize and continue the discussion without name calling.
You could paint clouds, or have a light that projects them 💁