Killer 2: If you know some vehicle or add-on will lag/crash you, then don't enable it at all. This also prevents you from having to ask everyone what they're spawning. (They majority probably wouldn't answer anyway)
Spencer 1: You just don't give people Admin, or Super Admin for that matter, if they ask. (In almost all cases) Although he may have seemed like a nice guy, you barely even knew him. This shouldn't be surprising. As for the weapons, basically the same thing I mentioned with Killer 2; don't enable bad add-ons, try taking out add-ons you don't need.