Sorry to dump and run earlier was still dealing with ds, yes he is going to be knackered tomo it's a long story i forgot to give him his sleep med 
I actually have sympathy over the food prep thing. Ds won't touch certain foods without protective gloves if they are raw, I can't abide the smell of meat cooking makes feel very sick so I literally freeze the house whilst cooking in winter. It makes life harder and is actually a pita. It is very hard to get over too so I really feel for you having to do the prep but I agree that getting an ASD to change long term trains of thought is really not something you have the time or energy if it were possible atm. So you are probably sensible to just do it MrsK BIWI did make a very valid point, with what you are dealing with most people would be over whelmed, over tired and struggling. You need to cut yourself some slack. It will get easier, eventually but you need to do the best you can and give yourself credit for this.
Are your two in a buggy when you are out, can you have some snacks to nibble whilst you are out even if they end up being your meal rather than what other people consider to be a meal. I know that some of my meals a lot of people would not consider a meal, but I will acknolwedge that I don't have a problem with feeling hungry, so it is probably not that easy. However, the concept of what a meal is, is actually a society constraint. Be reckless and define your own 