I think you went too much for the Stables - they are nice for your deck, so it's a tough call, but against an engine, especially Possession, you need a headstart on greening. E.g. on turn 9 you buy 2*Stables, but Province+FG would have been better. Your opponent's City plan would have been a lot slower if you hadn't done the work of emptying the Stables pile.