If there are no magic answers, so be it. I'll just brace myself and carry on. It's also a bit heartening to hear that my kid isn't the only one who does stuff like this, and it is as exhausting as it seems.
You are not alone! In fact, reading about your DS makes me realize that our DS has made some progress. So take heart, it does get better!
Early on (two years of age), we instituted the 'at least one bite of everything on your plate' rule and did leave things alone if he took a good-faith bite of a new food (as opposed to nibbling the tiniest possible micro-molecule etc). We continue with this. Even still, getting him to take that bite is often a 30- to 45-minute struggle. Seriously.
We try not to discuss it. We remind him of the rule and we remind him that there will be a consequence if he doesn't eat it. Maybe no Wikipedia searches that evening? I realize that we should try to use positive reinforcement where possible, but you also have to do what you have to do. We remind him that there are rules and they have to be respected. Once it's established, it becomes part of the routine. Of course, I recognize that it can take a loooong time to get there.
We want to be careful using food as rewards because my husband and are both very overweight. We use them, but we only give one food reward for every four non-food rewards (toys, Harry Potter chapters, supervised Wikipedia searches, etc) and are desperately looking to expand the non-food-reward options.
I get that one, for sure. We also use sticker charts at the end of which there is a bigger reward. Pokémon cards work well in our household.
Sometimes we do give him choices of places to go, but it doesn't always work. If given a choice between a place he knows and one he doesn't, he picks the one he knows. If given a choice between two places he doesn't know, he will refuse both. We get around this by saying he's going to go to New Place on X date and signposting it and foreshadowing for a week ahead of time. (We will sometimes ask his ASD therapist to write what's called a Social Story, which is just that--a story that tells what will happen on the day.) That prep usually kills any initial refusal but he'll sometimes refuse to go on the day and we have to deal with that tantrum and get him over and past that. (sigh)
Have you ever heard of Superflex? He has helped us through a lot of situations! You just need to google search. And also, the book Your Fantastic Elastic Brain really helped.
Good luck! We're in the same boat and it always helps to share these tips and tricks. Even if just one of them helps...
