1. Have not personally done this, but I have read that it is well established that you cannot get into that room. You may make withdrawals via the deposit slips.2. Go to the area marked "Black Pool". Just use an empty bottle on the pool. The below map is from http://www.volberding.com/Wizardry8/Wiz8Main.htm

3. Not sure what that is. There is a Bastard Sword and a Saint Bastard in the game and there is a plain Rapier.
4. I believe you just need to get a Mook Alliance letter from one or the other to get the CM. You can do this by joining either one or by killing off either one.
5. Not sure. I have read though that this is a necessary step for solo if you do not want to recruit NPCs to kill Brekek. So one would surmise that the kidnapping does not occur.
6. That's quite a question to ask, one which could be endlessly debated. A better question would be "how does this party sound?"
Personally, I think it is a pretty good party, though I am reluctant to go through a game without Alchemy (Ranger, Ninja, Alchemist, Bishop) as they are the money maker for the party.