D.K.
Amen to your DR! I agree completely. Three things you cannot force a child to do, eat, potty train and sleep.
HOWEVER, you can set them up for taking responsibility for eating. Do not give snacks within two hours of dinner, then he will be at the table hungry. Offer what the family is eating, period. Sit down as a family and eat. If he doesn't want to eat, that is fine. Let him get down. Put the unfinished dinner in the fridge. If he comes back hungry offer it back to him. Otherwise do not worry. They instinctively will not starve, they won't.
If he is filling up with milk, snacks during the day he won't have much appetite at dinner. Just don't play the game, he can eat or not. No biggie. It will and has become a power struggle, the less you worry about it he will get it, he has a choice. He will make it through without food if he wants to. Do not play into his fits, if he pitches a fit, get him down and say "okay, if you are hungry your meal is here".. and be done. When you take the power struggle out of it, he realizes he has control over being hungry or not, it will fall into place. Kids at this age vary with appetites, with teething and growth spurts too.
Reheat exactely what you gave him that he refused.
All kids have things they don't like, that is fine. Both of my kids have a list of like six things they just have tried and don't like. I allow that. Those things should be on a short list and don't serve them to him, however if he is being picky for no reason or just playing a game, don't buy into it.
Both of my kids grew up with this theory, some nights even my four year old just says "I don't want to finish I am done and I know nothing else before bed" and that is it. They know the rules, they are clear and I don't cave, THEY WILL NOT STARVE.
At breakfast and lunch, give him healthy choices to make up for not eating the night before, but set his snacks, meals on a schedule. Grazing during the day will start picky eating habits and throw his appetite off.
Wake up, eat breakfast, mid morning snack, lunch, mid afternoon snack and dinner. Serve milk during the meal and do not let him guzzle it down before he has eaten at least half. That is all he should need.
Good luck, don't cave and just serve what you serve and sit and eat with him.