in pic 2 and 3 he looks a little sickle hocked, but then in pic 4 -5 not.
He is not butt high. That wither is going to make saddle fitting difficult.
He needs top line work, and he could probably do hunter flat work, and western pleasure if you can get him to relax and round his back. He is a tad cow hocked but since you are doing halter classes and not doing cutting reining he should be okay. Love his color and his shiny healthly coat. Hope he works well for you . I would put a tad more weight on him , not whole lot , but a little more.