Will you ever do a collaboration with X?
Possibly. I have collaborated in the past but it kind of feels like the stars has to align right: Both people have to be on the same page, into the same style of design and have both interest and time for the same project. It is usually easier for one person to contribute something to another persons project.
Five Leagues questions
When exactly are pre-game potion use decided?
You can use them at any point during the setup sequence. For example you can use a potion after you have determined what type of enemies you are facing. It's not meant to be all that exact.
What exactly does it mean to survive a game for XP purposes?
A survivor is anyone that took part in the battle and did not die when rolling on the post-game injury table.
Does Morale apply in Site battles?
Yes but only to enemies in sight of the casualties.
General rules questions
Does a 6 always succeed and a 1 always fail?
Only if the rules explicitly say so. Parsecs and Leagues both do NOT use this for hit rolls. It is possible for a shot to be impossible or for a shot to hit automatically. (This is of course easy to house rule if you prefer).
I found an exploit!
For a game of the size and scope of Parsecs or Leagues there are probably a few. While more egregious (or silly) ones are something I track for future updates, I don't usually put a lot of priority in "blocking" exploits since they are 100% player driven. If you found a way to get infinite Credits somehow, ask yourself if the game would be more fun with infinite Credits.