99 won't crank any ideas?
 

I took the miata out yesterday for two 100 mile trips for the first time in 3 months. Now today it won't even crank. The battery has 12.49 volts. I tried jumping it, just in case it wasn't enough to engage the starter. No fuses are blown. The only difference between today and yesterday is 24 hours and 10 degrees F. I hit the starter with a hammer a bunch while a friend tried to start it. No dice. Checked the engine ground and tried to clean it up with a file. Still nothing. Is it safe to say it's the starter? What's the best way to test it and eliminate all other possibilities?

Useful info:
99 with 106k miles.
No weird wiring or anything, just remote locks and a radio (had this set up for 2 years and never had an issue with power drain and all wires are crimped and properly spliced)
Battery is a newish westco that kinda sucks.
Car is relatively stock except for FM clutch and FM clutch bypass switch.
Ecu is stock.

I would check the connections at the clutch bypass switch...

Check the starter for a cranking signal with the key in the start position. Or give that wire 12v with a jumper wire and if it cranks you know it's not the starter.

I didn't do any wiring, it's just a clip that pushes the clutch switch down. But I checked the connections and it's working as it should.

Tried that just now. Looks like I'm buying a new starter. Any brands to avoid? I'm going to grab one from rock auto or fcp import?