If you want to be sustainable about food and diet, the only real choice you have is cooking your food yourself from scratch. Buying frozen food is pretty much the same as eating at McDonalds. People picked on fast food so much, but not frozen/box crap.
Personally, I don't believe "carbs" are really bad. You could have some issues with it, but I believe it's more a case by case thing and not a rule that everyone is sensitive to carbs in general. Look at Asians, they eat tons of rice, and they're rail skinny. Since you're diabetic, you probably have an underlying issue of high cortisol causing it. High cortisol causes you to have higher blood sugar levels even without eating. Diabetes is pretty much intrinsically linked to stress in lots of cases. So I believe the low carb diets are a lot of times used as a bandaid for diabetes caused by high cortisol. It works, but it's not ideal in my opinion, and it's quite expensive really, doing things like eating a pound of meat a day and all that crap. I've done it, and I used to espouse it (if you look at my earlier posts, I did) but I pretty much got myself sick on a diet like that. I'd recommend for your diabetes, check with a good Traditional Chinese Medicine doctor, I've had good success using Chinese medicine formulas, and they're relatively cheap as far as medications go. Like $5 OTC at my Asian market. They might be able to help your schizophrenia and diabetes. It's worth a shot in my opinion.
But going back to the cooking thing, that's your challenge. Everything you eat has to be cooked yourself on a stove from scratch. Or at least like 90% of it. If you're not doing that, you're completely utterly spinning your wheels. As far as "what" you exactly eat, just think of a traditional diet of another country. Pick foods from Asia, Europe, what have you, most will work fine for you (as long as you don't have giant boreks or pizzas every night or something) be somewhat mindful of their nutritional content, but really, don't worry too much. You should at least be feeling better after that, and able to think more clearly, and probably will lose some weight.
As far as exercise, you have to find an activity you actually LIKE doing, and make it a hobby of some sort. That's the only way you can sustainably "exercise" as if you cared enough about your vanity to exercise, you'd have already been doing it. For me, it was figure skating, my sport I chose. I was 210 or 215lbs, a doctor at 19 years old had diagnosed me with high blood pressure (150/90) and told me "I don't think you can solve this just with exercise and diet alone" and to prove him wrong, I did. Within 4 months I got down to 180 with an hour of skating a day, and maybe 3x 45 minutes a week of the punching bag, and my blood pressure had normalized. The important thing is, to do something other than stay home. The exercise should be relaxing, too. No need to do some stupid highly intense aerobics or anything. Just walk around outside or something. Do something to relax. You're trying to defeat high cortisol here, remember. My next favorite activity after skating as far as how it makes me feel is hiking. Hiking, assuming you can get to a local park with some trails, is easy and fun, and you can go your own pace. In my case, within like 3 miles of where I live there's probably half a dozen or more places to hike. Even doing things like walking to the grocery store or something. But find some athletic thing you like doing, and do it everyday.