Keenan, there is no one foolproof thing you can do to prevent theft/damage to your car. If you want to deter it, here's a few simple things: locking gas cap and a locking hood latch. Locking gas caps are fairly cheap; you can fashion a simple locking hood latch using a bicycle lock cable. Route the cable through your hood latch and around a sturdy part of the car (e.g., bumper bracket). Pull the slack out and lock it up.
If you're worried about fire...well, by the time an engine/electrical fire gets far enough advanced that you notice it from inside the car, it's too far gone to tame with an extinguisher. Just get out and let it go.
If you want to deter total vehicle theft, here's a suggestion: splice in a toggle switch in the white wire that goes to your fuel pump, just before the inertia switch. Yes, that'll allow the vehicle to be started and driven; however, it'll only go as far as the fuel that's left in the float bowl will take it. At that point, the car will quit; the thief will then want to get as far away from it as possible. You can then start looking for your car within a quarter to a half mile radius.
There's also a pedal lock device that you can use to lock up the clutch pedal.
This all sounds better than a whooping and beeping alarm that no one will give any mind to. Hope this helps you out.