Should my second Amb have been Silver instead?
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Your problem was that you didn't Amb aggressive enough. T3 Amb is obviously correct, a Silver there would have been truly atrocious.
On T4 I'd take Farming Village over a second Tournament seeing that you have two Ambs in your deck, but Tournament isn't terrible. On T5 you certainly want a Farming Village over a 3rd Tournament.
On T6 your hand is Ambassador, Tournament, Estate, Copper, Copper, with Amb, Tour, Cop left in your draw. The best play here is to not play the Tournament and just return two Coppers. As played you absolutely have to return the two Coppers over the one Estate. The time to prioritize building over thinning is when you're drawing your deck and playing both Ambs each turn, and you're far removed from that point.
On T7 you again return one Estate instead of two Coppers, which is the inferior equivalent of clicking the resign button.