Hello S.,
I am sorry you are having such a time with your son. I have 3 boys ranging from 8-11 and I have been ( and still am ) in your shoes..
As you may know, our tastes change throughout our life.. I can remember when I was a kid, I hated certain things.. now, I absolutely love them. So, that's part of it, also, at the age of your son, it is a control issue too..
We worry that our children don't get enough nutrition and we want to force good food on them.. However, this may be a better approach.
With my oldest boy ( my most "finicky ) I put veggies on the table every night. He complains that he doesn't like this or that. My husband and I tell him this. You MUST eat 1 tablespoon of whatever veggie is on the table. or nothing later.. no deserts, no chips, no more meat from dinner. NOTHING. I will guarentee you he WILL be hungry. Don't yell though, Just be calm and tell him it is your job to be sure he is healthy. If he "has a fit" , calmly send him to his room to do that. He may yell, scream, ignore as much as possible ( don't argure back ). eventually, he may say " mom? ca I come out?? You tell him, well, do you feel you are ready to talk calmly? He may say "yes". Tell him that if he can not, he will be asked to go back into his room. Ask him what part of that food, he doesn't like. Maybe have a discussion about veggies he is willing to eat. Like, " I will tell you what. If you HAD to heat one veggie, what would it be... then make a deal with him. for the next 2,3 days make only that one. He must eat 1-2 tablespoons ( tell him ahead of time ). Maybe next week ask him is there another veggie you are willing to tolerate? Be sure to always talk calmly and lovingly.. don't feed that fire.. When he is NOT calm.. you decide not to converse with him. Always smile and tell him you love him, but that you are not going to argue with him. eventually, he will try a little here and there. Be sure you are always setting a good example too.. I found my boys ALL prefer RAW veggies, so most nights, I put a tray of carrrots and celery and brocholi on the table and put out the ranch.. If they don't want my cooked veggie, they may choose the raw ones.. I hope this helps.. A.