So I'll stand firmly behind my Trading Post open here. The reason I was so slow to build was for two reasons: first, I neglected to buy a Spice Merchant on T4, which was pretty stupid. The Trading Post needs to be pretty quickly followed up by a Spice Merchant (Why can't I open with both? Man, Dominion is hard.) and probably more significantly, my Trading Post missed two shuffles the first two times I saw it (if it had been a Spice Merchant I would have been just as screwed). I really like the way you build up this game but I think it could have been better with a Trading Post in there. It probably isn't a huge difference.
I said this in the video, but I think you needed a Catacombs or two before you ended up getting yours -- also, I think you needed that unique card for your Fairgrounds, so I don't know if Duchy would have worked for you there. Maybe it would have?
In any case, you were for-sure a favorite to win once the GMs were out, I was playing to my out that you would stall (could that have been prevented/mitigated with some more Catacombs? Doesn't look like it but it probably would have been preventable if you hadn't started to green that turn, I think) and it came through for me so that was pretty lucky. The interesting thing about this is that I was in a favorable "endgame dancing position" every time I had a turn.
What does this mean? On T12 you buy a single Province, which allows me to leave 6 Provinces in the supply and add a Catacombs that my deck desperately needed. Double Province would have been a fine move for me there too to leave 5 Provinces in the supply. Why are these good numbers to have? Well look at the situation it puts you in -- you really want to triple Province with your deck, but you give up win equity if you do because at that point I can threaten to triple myself and you have to play around that.
Because you stalled on T13, I'm able to leave 4 Provinces in the supply and have a decent lead, which is a huge asset for me. You don't really have any good moves at this point.
Have you ever played that really old game, where there are 13 pins in a board and each player takes a turn removing either 1, 2, or 3 pins from the board; then the person to take the last pin wins the game? The first player can force a win by always leaving a multiple of 4 pins in the board at the end of his turns. Now that helps you have the last turn of the game so Dominion is a little more complex, but this analogy has really helped me to understand favorable endgame positions in Dominion.
I should stop rambling, I don't know if I'm going anywhere.