As to your question about the amperage of a switch, I'd pick a switch that will handle the maximum current you plan to use, in this case, a 60+ amp switch rated at 12 volts.
As you know, switches have an amperage rating based on various voltages. As the applied voltage goes up the current capability of the switch goes down, and vise versa. Just watch the current rating for a 12 volt switch (since that's as close to 14.4 volts as the specs will get) and reduce the amperage by 2 or 3 amps to make sure get what you need.
Now, this is assuming you'll be pushing the full 60 amps through the switch. If your system actually draws less, then a lesser amperage switch will do just fine.