I'm not sure if this will help or not.
My DS1 is a young adult now, he has no diagnosis but we were told that we could pursue one but it would be borderline. He was similarly difficult to feed, from babyhood onwards really.
The good news is that his diet is much more varied as an adult but the foods (mainly vegetables, certain things touching, anything "damaged") that he was particularly averse to are still an issue but we've managed to move on with many others and many "new" foods and some things are now fine to touch.
For example, he wouldn't eat chips or potatoes. He would eat crisps, so we moved onto very crispy thin chips or slices of potato, to gradually thicker chips, then very small roast potatoes to increasingly more potatoey chips and cooked potatoes and now he'll even eat mash and potatoes in virtually any form. Same for chicken nuggets up to chicken which he'll eat in all forms including on the bone and also just tried random stuff, most of which has worked but some that hasn't. He wont eat veg but will eat pretty much all fruit and he'll have beans, mushrooms, onions and cooked tomatoes as long as they don't have lumps and he'll have carrot in bolognaise if it's grated and he does know it's there, so not hidden.
His turning point was when we stopped tricking him into eating as a toddler and he went a couple of days with just milk and snacks (like cheese strings) and when his back was turned, he's gotten a spoon and tucked into DHs beans on toast which had added tabasco, soy sauce and HP sauce. He just prefers spicy or strong flavoured food. So, for a while we had a child that wouldn't eat chips but would sit and eat a tin of peppered mackerel!
I guess what we did was find flavours he liked and added them to different foods e.g. like teriaki, so now have that with salmon as well as chicken and so on. Except he still won't touch the vegetables no matter what we smother them in!