I encountered this singing bard named z-axis who told me about his wanderings and search for his sister. Apparently I had picked up a note telling of his sister's demise and he requested to join our group to avenge his sister's death. I felt bad for the guy so I couldn't deny his request for vengeance, but now that we've destroyed the temple, I don't want to share experience points with him anymore but I don't have any dialogue options to get him to leave the party. Is there a way around this?
Go into combat mode and single attack him to death. For the more lawful among you, just get into a moderately challenging fight, send him up front, and sit around while the monsters kill him for you. Then just dismiss his dead body from your party.
Just right click on him to open the radial menu and click Talk. It gives you an option to dismiss him.
Right clicking on him (Zaxis himself) and choosing the talk option lets me use him to speak to someone else but it doesn't give me an option to dismiss him. If I use one of my 5 starting characters to talk to other npcs (like Meleny) I can dismiss them from the resulting dialogue options. This is true of every NPC I've had in my party save Zaxis.
Can you move PC's to different slots? What if you have 8 PCs and want to move the last two spellcasters to a better position for map changes/transitions?
Krag- Clickhold and drag on the portrait in the party roster in the bottom left of the screen to move party members around, if that's what you're asking (similarly you can move characters to the right in the initiative order at the top during combat if you wish). But a party only has as many slots as party members, so you can't put someone into slot 7 if you only have 5 characters.