Yo, I have exams so I don't really have time for these atm. sanni that's a Halo bug, if you spawn vehicles to map with no vehicle spawn point the server will crash. But as it was mentioned by Rob, setting the vehicle respawn time to "never" should fix it. And 'me' + '#n' should work at the most of case, but only those commands have player expressions which has "player_expression" as first argument, so not like spawn.
Oh and for that sv_password thing... I'm just using an event_leave $pn=0 'sv_password ""' to reset the password when the last player leaves (event leave doesn't get executed at new game when the players just leave and rejoin). Or you can use event_leave $pn=0 'reload' to reset all server settings to "default".