Hired and experience-sharing (Neverwinter Nights)

I want to go through all the campaigns without the hireds, but there is very lack of opportunity to open the locks and remove the traps.
(In some cases, it is possible to break the chest or door, and the traps are simply taken for granted or, if on the chest, they can be shot from afar.)
But often come across chests on which weapons are simply ineffective.

That's why I'm thinking of hiring a thief for such simple works, without fighting.
However, he will be a member of the party, so he will have enough experience:
1. Experience is divided among party members equally or somehow proportionally (level caused by damage, ...)?
2. If someone did not participate in the fight, experience is given to him? For example, I just left someone in another location, ordering to stand still, not driving out of the party.
3. If I removed the recruit from the party, then he can be hired again (where will he be?) or will he disappear forever?