I'm running 12 guage with a weather proof 3amp fuse.

12-gage is plenty heavy enough. 16-gage would do it. There's nothing wrong with wire that's too heavy, that can't hurt anything; it just has to be heavy enough.

Nobody has discussed the location of your fuse, however, and that is important. You want to locate the fuse as close as possible to the battery, and absolutely, definitely between the battery and the firewall. This is because the most likely location for a short is where the wire goes through the firewall. If the fuse is located past the firewall, when the wire shorts there is no protection and the whole wire between the battery and the firewall goes up in smoke, taking other things with it, possibly the whole car.

tanstaafl.

"There Ain't No Such Thing As A Free Lunch"