His starting skills are quite good. I like his respectable passing.
Well I've never trained a big-men in my BB career, but I think I'd start off with rebounding. Maybe 3 weeks of rebouding, followed by 1 week of IS and 1 week of ID. You can repeat this procedure for the whole season. But also, you might want to train FT as well, as atrocious FT is very very bad. When the FT skill becomes pitiful, the chance of making a FT increases by about 10% from my experience.
I don't think he could be in U21 NT team, simply because he's already 19 year old and there must be many other big-men with far better skills than your players, who are 19 year old. But he's a nice rookie with good starting skills and fantastic height for big-men.