Okay, so with Goons allowed, but no Monument, Bishop or Ambassador to prevent infinite scores. Here is a first attempt.

...Wow, this is crazy long. (It is a bad habit of mine I suppose.)

If my counts are correct, there are currently 135 different cards in the game, and 119 of them are actions.

Our Kingdom is:

1. Gardens

2. Duke

3. Vineyards

4. Fairgrounds

5. <Any Action>

6. Goons

7. Shanty Town

8. Bridge

9. Black Market

10. Young Witch

B. <Any Action Bane>

In my previous post, I came up with 89VP tokens max in the process of buying 9 Shanty Towns and 10 Goons.

Since there are only 8 cards in VP piles, we have excluded Island, Nobles, and Great Hall from the Kingdom, because we get 20VP from buying 2 more cards with Goons which is more than the 16 (or 8) they provide.

We have 7 action cards in the Kingdom for a total of 70.

There is a total of 119 actions 4 are prizes and 108 are in the Black Market for a total of 182 actions for Vineyards.

There are 135 total Kingdom cards.

5 treasures, 4 Victory cards, and Curse add 10 to the total unique cards for Fairgrounds to make 145.

There are 7*10 action and 4*8 victory cards in the Kingdom.

Since we can't use Ambassador, we can't get our opponents cards. There are 53 Coppers and 11 Estates to be had.

There are 40 Silvers, 30 Golds, 12 Platinum, 8 Duchies, 8 Provinces, 8 Colonies and 5 Prizes.

135+70+32+53+11+40+30+12+8+8+8+5

This totals 412 cards for Gardens. We need at least 1 Curse for the Fairgrounds break point, so we should grab 8 to hit 420 so the Gardens break point offsets all the negative points.

Total of 420 cards for Gardens.

The easiest is 8 Duchies for Duke.

Starting with the 420 cards that we will ultimately have from Gardens, we have 5 prizes that we can't buy and 9 Shanty Towns, and 10 Goons that we buy before we get 10VP per buy. This drops us to 396 cards to buy with Goons, but we can buy two Curses we don't want to finish with at some point, and then Trash them, so that puts it back up to 398.

That should be all the pieces. The score is:

2VP * 4 (Island, Great Hall, Nobles, Harem) 8

1VP * 11 (Estate) 11

3VP * 8 (Duchy) 24

6VP * 8 (Province) 48

10VP * 8 (Colony) 80

8VP * 8 (Duke) 64

42VP * 8 (Gardens) 336

58VP * 8 (Fairgrounds) 464

60VP * 8 (Vineyards) 480

-1VP * 8 (Curse) -8

10VP * 398 + 89VP (Goons) 4069

Total: 5576VP

(To make it like the original problem was, we add our opponent's 3 points, and then 1 to get the impossible score of 5580VP)

Now... I did this all with the 3 forbidden cards still in the Black Market, but just not allowed to be played. That probably isn't right, so if we actually take them out:

We lose 3 actions -8 Vineyards VP

We lose 3 unique cards -16 Fairgrounds VP

We lose 3 cards -8 Gardens VP

We only need 1 Curse to reach our Gardens break point -(-7) Curse VP

We buy 3 less cards -30 Goons points.

The new total is 5521VP (and an impossible score of 5525VP)

Doing this makes me think there were a few mistakes in ghostofmars numbers (possibly done before Walled Village?), so I might try to re-run the original problem later.

The OP never did confirm a solution he thought was correct for the second question.