Just a quick rules question in regards to the rebel mission tokens. They heal 6 + insight successes worth of strain. Would this flow over to health as well? (because no one has over a 6 endurance)

Depends on the exact mission wording, i.e. "what is heal?"

If it says "discard X strain tokens" like Murne's card then no, it does not overflow into health

If it says "recover X strain" like Fenn's card then yes, you may get rid of damage as well

RRG "Recover": If a hero recovers more strain than he has suffered, he recovers one damage for each strain he cannot recover.

Just played it.

Yep, it flows over.