You know, I’m fortunate with my wife. She’s always eaten pretty healthy, and is still around 115 lbs. (only up 7 lbs. from our wedding 18 yrs ago, which is something I cannot claim). While we eat healthy and pretty low-carb, she still needs/wants sweets around, like cakes or doughnuts. At first, she would hide them so that I wasn’t tempted. I would find a box of doughnuts hidden in one of the cabinets. I have now developed enough will power that I don’t cheat very often, even when there’s a freshly-baked cake on the counter.
As for the lack of support, I believe the key is how you communicate. You won’t be able to have these discussions if you’re angry when you start. Plan out in advance what you want to say. The key points I would make would include telling them that you want to be around and live as long as possible, and that to do so, you need their help. Explain that you need to eat differently than you have done in the past in order to manage this disease that you will have for the rest of your life. Ask them for ideas on how they can help, and if that means separate meals, tell them that cooking two different meals takes twice as long, so if that’s what they want, they’ll have to share in the cooking responsibilities (which in my opinion, should happen anyway).
If you try to start this conversation while you’re angry, I think it is less likely that it will go well. Think in terms of helping them better understand what you’re going through, and hopefully that conversation will go smoothly.