1. A big school can support full-time teachers. A full-time teacher is probably better than a part-time teacher for obvious reasons.
I'm not so certain. I can think of at least one shihan who has been emphazising that one should have a life (both professionally and personally) besides Aikido. I believe it to be an important part of growing like an individual and something that you can hang your hat on, if training for some reason fails your for a while.