Heya, sorry it took me a bit to get back to you, had a lot of stuff pile on top of me on return and I forgot.
In response to your first questions, my intention with the game was to continue to roll on a failure, losing dice with each failure until I was out of dice (i.e. dead).
Regarding your second response/reminder, the Joker represents that you have completed a mission if one was generated at the start of the game, so yes you basically declare success for that run (or keep playing if you rolled 2 missions).