No prizes, answers published later on the author’s web site. The joker is there so that the 7th card isn’t too easy, though I suspect there are people here who could tell you which deck it came from.
part 3, I agre with you on 5 (and 1). For 6: I think it’s one of the objective cards from one of the Railroad Ink Challenge boxes. My wild guess at 2 is Who’s First, I think it is, a deck of first-player rules.
In Round 1 I got a card from a game I don’t own (Bohnanza) and failed to get a card from a game I do own (Jaipur), in Round 3 I got a card from a game I’ve never played (Ark Nova) and failed to get a card from a game I have played (Ticket to Ride).