Victor questions

[Pred]

If the Card is already in play then put a number counter #2 on that card showing its effects are on two people.

Yes you can use a first aid kit, its not affected by trade

why would a hero be needing keys during the zombie turn? but to answer the question, I don't see why not
(keep in mind though, that a locked door only counts for the first person going through that door. If a different character comes in behind that character he may enter that door without keys. UNLESS you have growing hunger (which I don't have, it'll be here tomorrow) witch I think has a different locked door that you haft to have keys to unlock it. (I don't know that for sure, I just remember playing with Mr Onearm and he had locked door tokens, that LNOE doesn't come with)