I'm going to agree with what JMac13 said (for the most part), but I'll answer your questions too.
How good is he defensively?
On the penalty kill, he's above average. He has a high hockey sense and he does a good job of getting his stick in passing lanes to disrupt flow. He also uses his speed well to forecheck a man down. Once he gets stronger along the boards, this part of his game will improve even further.
5 on 5, he's average. As JMac13 said, he has lapses where he becomes offensively centered. But at other times, he's quite strong on the backcheck. Again, he's a very smart player and I think he'll profile as an above average defensive player moving forward.
Is he good at faceoffs?
He's improving. Right now he's average on faceoffs. His teammate Alex Friesen is one of the best in the league, so he has a good mentor.
How is his skating?
As JMac13 said, he's an above average skater with elite acceleration. He can handle the puck at top speed, which makes him even more of a threat.
How is his vision?
While he's got an excellent shot, IMO his vision and playmaking are his best assets. He moves the puck so well, once the offense has set up in the zone. While most people think of him as a dangerous player off the rush, he's more dangerous when things slow down. He moves the puck very quickly and he catches defenses sleeping quite often.
How is his hockey sense?
He has elite hockey sense IMO (as I've mentioned)
From what I have seen, he is a pretty decent skater, with average size and a GREAT shot and nose for the net. The Avs could use another dynamic threat up front, especially a right handed one.
But, do you see him long term as a center? Is there any way he could be transferred to play the wing?
That'd be a waste of his talent IMO. He's a naturally gifted center who's biggest strength is his ability to create scoring chances for his linemates.
Where do you see him going? I would expect somewhere in the 5-7 range possibly.
Right now, he's a serious candidate for the OHL's Red Tilson Award (MVP). I think he's a serious candidate for the top 5.