(((((hugs))))) he will not let himself go hungry. If he is not interested in eating, just get him down from the chair. Give him a small snack at his usual snack time, and then offer him a proper meal at his next mealtime. If you give extra snacks and extra milk when he refuses a meal, he still won't be hungry to eat!
Other things you can do at meal times include giving him a spoon so that he can try to feed himself. Yes it will be messy. With my LO, I would have two spoons, one for him to try with, and one for me to put food into his mouth in between his tries. Also sometimes I would load up a spoon and put it in his hand so he could put it in his mouth while I loaded up the second spoon.
Another thing to try is finger foods. My LO never ate sticks of food, but he loved using his pincer grip so blueberries, halved grapes, cubes of cheese etc were good. They would keep him occupied sitting still, and I could feed him while he worked on his finger foods.
Try to relax. I promise you, he will not let himself starve.