J.G.
I agree that a second opinion is a great idea.
But also, you're the mom and you know you need to fix this now. He can't eat three things his whole life. My only suggestion - you said you can't stand to starve him - yet at the same time, you said you're desperate. My son is 22 months old. If he doesn't eat what I serve him, he doesn't eat. He's learned that and he hasn't refused many meals. I always put at least one thing on his plate that he knows he likes, and add the 'not-so-favorite' next to it. Also, sometimes he asks for Ketchup and I squirt him a bit so that he's happy and more likely to eat more.
Also - does he see someone else being really picky? And if he's never been denied his favorites, then he's learned that he can get his way if he throws a fit and you're perhaps enabling him. Sorry if that's not the case or if that sounds mean. But you're his mom. You're allowed to tell him no, he's a kid - so he's supposed to get mad and cry. You won't scar him for life making him eat some chicken. You'll scar him more by not fixing his diet now.
Good luck.