wow. Lot of questions. And we're starting to move into the realm of the server area here.
1: Leopard has what I regard as a bug where it doesn't use kerberos credentials when connecting to certain SMB shares via the Finder. If you look in your logs on the client you might see a message saying "Server doesn't support kerberos but you are requesting kerberos". Please call Apple and file a bug report so maybe they can fix this one of these days.
2. This bug is not present in command line. If you use login scripts you should be able to avoid this.
3. /Library/Preferences/com.apple.dockfixup.plist is your enemy
4. Create your mouse preferences. Open workgroup manager, select your directory node, select your group, click on preferences, click on details, then click on the + sign to add in mouse preferences.