This is a big/fraught question: where's the line between a strict diet and disordered eating?

Dh and I have been having an ongoing dispute about this. I'm someone who believes in moderation, but dh is kind of an all-or-nothing guy. For months now, he's been on a keto diet: no carbs, including limited carbs from vegetables (like, tomatoes are suddenly the devil), and high protein/fat. It's REALLY extreme, imo. He says it's making him feel better and he's been losing a lot of weight (prob 20 lbs so far), and that I'm just objecting to it because it's not convenient for me. He says he is doing this long-term. But, I just find it so restrictive, especially since it's almost the opposite of what I eat--I'm a vegetarian, so it's impossible for me to eat this way. Throw in a picky toddler (and baby, but she basically eats anything, for now), and it's really untenable. In my opinion. But he's the main cook in our family, so it's hard for me to tell him that his cooking isn't working for the family since the burden is already on him. His opinion is that it doesn't effect me if he's making food for me too, so why do I care, but it makes me sad too that our meals aren't communal right now. We don't even eat the same veggies! And, I feel like he's just become so obsessed with this diet, he spends a lot of time looking up recipes and supplements, cooking separate meals, etc. He's also really defensive about it.

I want to be supportive of his health but...this just seems so extreme to me. I'm really concerned about how my girls approach food/eating issues as they grow up, I want them to eat to feel healthy and strong, not worry about carb content or if specific foods are "bad" or "good." Lo1 is 4 and already asking about if specific foods are "healthy" or not, and what vitamins come from what foods. She's so observant and notices that dh and I eat differently. I suppose I'm being a hypocrite since I AM a vegetarian, and that is a restrictive diet, but I've been one since I was 4 and it's not a health/weight issue for me.

Am I just being a brat, or would you be concerned too?