I thought he was slightly cow hocked too, but not sickle hocked. He looks nice except for that third pic of him. I don't know if they are standing him on a hill or what, but looks really downhill there.
He is a three year old. He is pretty much what he is.
What would you like to train this horse to do? Higher levels of eventing he might not make due to a general lack of bone. He will have some difficulty with the dressage phase simply because he is down hill.