15...Kb8 may have lost you a tempo, slightly.
Truthfully, I probably would have played 15...Nf6 to get some more material out there, or perhaps 15...f5(with ideas of gaining some space and power over the Kingside.)
But, if you wanted, 15...a6 is playable.
I'm playing as black.
This game frustrated me so much... The guy did the pawn sacs in Danish gambit, in addition to that I even won a rook for a knight, but then he started attacking my king and I lost everything I'd gained. Need help with how I should have been thinking.