Hey NiftyHat! Great questions, I'll add them to the errata doc.
1) Yes you may.
2) All equipment stacks, yes. This can become very broken very quickly.
3) After, tho before is an interesting idea.
4) I think changing their character sheet is a reasonable interpretation of that rule. Equally so would just be a character change too, emotion, goals, internal philosophy, loss or gain of loved ones, etc.