I started a forum on 9. b4. What was said there was that after 9... e5 10. b5 exd4 (rather than your 10... Na5? 11. dxe5 Nxc4 12. exd6 Nxd6 13. Qe2 where all of White's pieces will become better placed than Black's.)
Then IM pfren's 11. exd4 Na5 with a perfectly okay IQP for White, however the b5 pawn is a weakness rather than a strength. White will have to play some kind of minority attack with b6 or a5-a6.
I have to agree. 27. Rc3 was better, blocking the third rank, after which I can just advance my pawns.