Additionally, black market can add some. There are 53 2-cost cards, but 6 are events or heirlooms, so 47. With the 1 imp gainer, you have 39 2-cost cards eligible for BM, making black market an increase of 29 cards or 58vp.
BTW, are there really 47 2-cost kingdom cards?
http://wiki.dominionstrategy.com/index.php/Dominion_Card_Glicko only mentions 41 as of 2020 (42 "0-2 cost cards" minus Poor House). Since then, Allies has added 3 new $2 cards, but the 2E's of seaside and Hinterlands have removed another 3 $2 cards (replacing them with more expensive cards), so the total number should remain 41, not 47.
Edit:
There's also the non-kingdom card Bat at $2, which you could get from a Black Market Vampire.
So if you allow Black Market as Way of the Mouse and put Masquerade, Shepherd (for the 3rd $2 Heirloom Pasture), Young Witch, the Imp gainer, Vampire and all other $2 kingdom cards into the BM deck, you could get
Card Number of $2 cards (including starting cards)
Bauble 10 (+any number of Favors)
10 other $2 cards: 100 (including Pixie, Tracker)
Estates 30 (12+6*3)
Imp 13
Heirlooms 18 (6*3)
BM deck 31 (41 - 11 $2 kingdom cards +Bat)
-------------
202 $2 cards, for 404 VP