Q2. Player A plays Blackmail on a Player B character, and uses that character to attack another character in Player B's conspiracy. Does that count as Player A's one attack against Player B for the turn?
That's the single most common OnTE question ever.
No. The attack you make while playing Blackmail is not the one attack you get against them per turn.
I'll be putting up a session report soon.
I look forward to reading it.