I believe you meant Dual, as a duel is single combat between two opponents, rather than using two things at once.

Also, is maximize intended to stack with the empowerment, or replace it?

Nitpicking aside, I tend to just assume you've got it right, the amount of ToB homebrew you've done, and I don't see anything glaringly wrong here. Bookmarked for further use in case I ever play a martial adept, as always.