This gambit is a little above my paygrade. It looks to me like you had to take the draw after the threat of the queen trade. Although white is slow, black just can't do enough damage with the rook and bishop I don't think.
Keeping the knights instead of trading might have served you better. Perhaps 16..Nf6 17. Qh3 Ng4, and you have all sorts of threats with knights and bringing your dark-squared bishop into the game on either e5 or d4, or O-O-O. Just some random thoughts on a very interesting gambit!
What do you think?