i think the majority of people have a huge shift in their relationships when the first baby arrives.
sounds like this feeding this is getting to you both.
some children are thin, that is they way they are made, and the way they are, and will be thinner adults too.
some children are far too busy explroing and running around to sit and eat 3 good meals a day & 2 healthy snacks.
as long as he is healthy, i would take a step back, and absolutely stop running around after him whilst he plays, with food.
toddlers eat if they are hungry. and if he thikns it is a big game, he will keep pushing oyu, and enjoying all the attention.
is he vomiting becasue he is choking?
is your DH bothered about your son's weight? if so, why is he concerned you are overfeeding?
give your son 3 meals, and if he doesn;t eat them, then take them away, and let him get down from teh table, don;t make it a huge battle ground.
and sit down and have a long talk with your DH, and get to the root of this, you might be at cross purposes, and need to talk, rather than him presuming you have done something wrong, and you presuming he is blaming you.
also, no harm in getting a second opinion re your sons; vomiting if it is a worry.