I wanted to return 2 cards, but a lot of the time I either wouldn't get them or doing so would mean getting another Silver instead of HP and I already ended up with really too much Silver for a deck like this IMHO.
So yeah, I see how Quarry works here now, thank you. I don't really know what I was thinking about being ahead in the Amb war... must have somehow deluded myself into thinking a turn 1 buy is meaningfully "ahead" of a turn 2 buy or something. At turn 4 it seemed like I wouldn't need a second Amb (and I figured I didn't want one if I didn't need it because I figured an HP-rich deck eventually collides terminals a lot - but that's silly; winning the war early more than justifies a dead card late), and turns 5 and 6 I hit 5 and wasn't about to turn down HPs. But I'm still confused as to why the HPs did such a bad job of drawing and hitting 8. Maybe I should get more Menageries over Silver? Get a second Gold anyway since the deck drawing thing just isn't reliable? Oh, I suppose that plan really only works with a terminal-Silver Action? x.x
Extra Silver is not THAT bad. And you can always choose not to buy anything at all -- that is indeed a valid option. But you really should be aggressive in it. Your very first play was only returning the single Estate. Having it miss the reshuffle was bad luck though. You need to turn down the HP in the short term so that your deck is better in the long run.
Yeah, it's hard to get the HP stack to hit $8 if you're missing the last piece. Standard HP decks aim to draw Copper-Silver-Gold-X to reach $8, where X produces at least $2. Possible choices in this kingdom are Cache, Counting House and Hoard. Quarry can work (because you will usually pull in a second Copper or something) and Trade Route is possible as well. TR might actually be one of the better choices, actually, because it is cheap and it gets you +Buy.
Hoard is a fine choice. It gives you $2 and it produces more Gold, which is not a bad thing (especially in a slim deck like your opponent's).
Upon review, I think I might have tried skipping Ambassador altogether. What about opening Quarry/Trade Route? The opponent's Ambassador would ensure TR produced at least $1 to start (andif they skip Amb too, it's not like it's the end of the world). Rush Hunting Party (just like you did). Use the TR to eat the Estates and Copper that your opponent is throwing at you, and brush off the rest with mass HP. The +Buy should help, especially paired with Quarry for easy double HP turns.
Pick up a Hoard ASAP. Use it to buy a Duchy and get your first Gold, bumping up TR to $2 and maybe trashing the Duchy with TR later if your HP stack can't handle it. TR should eat the Quarry at some point as well. With a big HP stack (I mean, you got 7 of them!) and TR you may be able to pull off some Province-Province turns. Province-Duchy, certainly (but only if you have enough HPs to draw past Duchies).
It always feels weird to skip Amb, but I think it might be OK in this case. I think it hurts more to try for Amb and lose. But skipping it altogether here seems viable to me. Am I crazy?