1) Yes, mercenaries are very difficult to hire in any region that the AI is active in, and I often battle full armies of mercenaries which would indicate the AI is hiring them quite a bit.

2) I want to say I have had a unit charge without orders, but if it does happen, it is rarely.

3) I couldn't say, sounds like one of many vista-related issues.

4) I've never used it but I did have problems using the move_character function until I figured out how to type the names correctly. Marcvs Jvnivs Brvtus beomes "Marcvsjvnivs Brvtus".