I'm certain that there are several threads about this floating around. Your solution can definitely be beaten.
Your solution also is not infinite, because it fails if you don't reach your SP.
That's easy enough to fix though.
Ambassador is not necessary, and it's a bit of a hack anyway because it only really works in solo play.
Instead, empty the Silver pile. Include Black Market. Inside the BM, include Young Witch so that you open up an extra Kingdom pile. Also include Trader, Scrying Pool and Scheme.
Definitely have Goons in the Kingdom. Use the rest of the Kingdom and BM to get as many Buys as possible. Probable cards to use include:
King's Court
Throne Room
Squire (+2 Buys each)
Princess via Tournament found in the BM
Festival (because you'll be wanting those extra actions)
There is a challenge somewhere about getting the most possible +Buys, I think. Note, you should be able to get more than 42 buys fairly by using KC on +Buy cards instead of Ambassador.
Anyway, you can easily spend all your +Buys without ending the game by buying Copper, revealing Trader and gaining nothing because all the Silvers are gone.
Use Scheme on Scrying Pool to ensure you can play all your cards every turn.