Again, you can be running 100 amps worth of accessories but your ammeter will be showing only an amp or two of charge into your charged battery.
There's something wrong here. Assuming you have your rig wired like it came from the factory the amp guage should barely wiggle when you rev the engine when the battery is charged. Are you using the original wiring or is it an aftermarket wiring harness? I suspect the ammeter is wired into the circuit in the wrong place. There's no way you should see that kind of current flow into your fully charged battery!!!
Your fan sounds like it's wired correctly.
I guess if you want to run a 100A breaker you can but I shudder to think what might happen if it tripped some night while you were coming down Kingsbury grade!