I trained Yoshimo up to a lvl17 bounty hunter, is there no way to stop him attacking u in the asylum? and get him to join u again? i f he dont i have not got a thief worth anything!

Nope, no way. People who read ahead on the boards usually opt for Jan becuase of this, but that is no fun.

Imoen is fine for you for the rest of the adventure - her trap skills are great. You will miss the backstab and set trap abilities though.