Further to your questions regarding the Joker, maybe give him a X number of kills? like 4 or 5?
And then he can choose to kill both targets, 1 target, or neither?
That way, the Joker isn't confirmed if he selects himself. Or, he can frame someone as Joker, ect.
I do think that the Mafia should get a Factional NK if the Joker dies.
I think Joker shouldn't start with a bomb, but just my opinion.