Math.... I should have done it!
35 watt low beam + 55 watt tractor light = 90 watts. 90 watts / 12 volts = 7.5 amps.
55 watt high beam + 55 watt tractor light = 110 watts. 110 watts / 12 volts = 11 amps.
The headlight fuse is 7 amps. Apparently when I was testing the tractor light, 7.5 amps was not enough to blow it.
So I'm out in the middle of nowhere. It gets dark, so I flip on the high beams, then throw the switch to tie the tractor light into the high beam circuit.
Turns out that both of the spare fuses in my fuse box were blown.
So I swapped in the fuse for the running lights and stuck a paper clip into the front brake switch so I'd have some tail lights, and got it home.
I shall have to install a relay and an aux fusebox.
Moral of the story: Don't be derpy, and do the math. :P