nightstalker,
Most of your questions can be answered by doing searches and reading.
The simple answer is yes, at least for short periods. I've run it successfully with 14.4 volts and 8-10 amp loads. However, lamps run at those levels make lots of heat, and the switch IS plastic, so be careful.
It helps if you lower the resistance inherent in the switch as much as possible by improving the contact points with ProGold, hard wiring any spring contacts, etc.
Bill