1) Yes you can use him because he 'll gain more than a practice match/3 bars. At the beginning, use him only in non critical games like against easy opponents in League or Ch. League groups.
I suggest to leave a 3h resting period after the match and then train him. Don't trust green packs.
2)Aerial is good
3)DR is good for being a great defender (giving sp to Defense and M&P) because DMC needs sp in Attack too.