I would have gotten an early salvager instead of a lookout and open silver spice merchant to buy minions earlier here. Salvager helps to hit 5 as well while lookout does not. The question of how many silvers is a good one, but because also of spice merchant 2 seems optimal. You will hit 5 even without the third. An earlier outpost would look nice, at the point where you are sure to hit 5 on your main turn even with outpost in your deck and maybe hit it with a 3 cards hand. I think this is the point where you have 3 minions in your deck. Regarding the province trashed, i think it would have been better to not trash the minion at all and just buy a duchy. You should have expected 3ple province from your opponent at this point. Regarding how to think about your last turns, keep in mind that outpost perplexes the endgame.
Eventually this becomes a question of how often I expect to miss buying province if I do not build further vs how often I expect to reach double province, or will i reach double province when I need it? Building further for a total of 3 turns to reach double province by buying a market, then 2 markets, then another 2 or 1 and a small bonus seems a bit slow to me, but could be best here, if the path to green on your outpost turn was not successful often enough.
Going for a double province turn with the outpost (buy 1 province at a normal turn and 1 at an outpost turn) seems best, even if it does not always work. The way I can see it is by playing 3 minions on your outpost turn for coins, 2 to discard and draw and hopefully you use your silver or your salvager on something, as you have enough salvager food after turn 10. So assuming you reach turn 11 with your deck, I would buy an outpost turn 11 and turn 12 and beyond province and a salvager at the first turn I miss province.
Edit: Looking at it again, it seems like trashing the minion and buying province is best instead of buying a duchy as I proposed. Reaching 13 to buy province duchy next turn for CIM is not as likely as I thought and so it is difficult for him to get 2 provinces 2 duchies and an estate for the win.