He looks okay. You do not want back bones, hip bones etc sticking out . A few ribs is okay as long as there is flesh over them. As He grows he will change body shape. He will also be building muscle so he needs to be in an area where he can move around and use his legs and feet. Be sure to keep him up on his vaccines and farrier. He looks like he will be a pretty horse. I would not really use any sweet feed and he should do fine on good quality hay water and mineral/salt licks.