Interesting: normally white castles king's side o-o so as to use Rf1 as support for f4-f5.
After your 12 g4, he could just take your pawn 12...Nxg4. You get the open g-file, but he trades off your valuable bishop that you need for an attack.
With 14...b4 he could have profited from your unsecure king's position. I doubt a3 and o-o-o is a good plan. In the open Sicilian white plays o-o-o, but will refrain from a3 and will often play Kb1.