I agree with most everything except Kimmimaro. Yea Kimmi is awesome at taijutsu, but Lee is great as well. Lee had no skill in anything but taijutsu while Kimmi had a KG. I would give him some props for competing with him.
Exploding tags could have been A. Been ordered; or B: could have been stockpiled. ...C. Summoned from somewhere. (See 'A' mention).
As for the boy mention... He had the advantage of surprise. No-one would had been expecting such from a meere child. Not everyone will be on their toes with every (considered) victim...