Couple observations.
1. If you think your insurance won't pay market value in the event of a total loss, find a new insurance company.
2. Steering wheel locks are for show. Takes about 10 seconds to cut through a steering wheel, making the "hardened steel" lock nothing but an awkward shaped club.
3. There are several potential components I could think of wiring a cutoff into. Power to the FCA, power to the lift pump, are a couple. That said, I wouldn't really want to cut into any of the OE harness if I didn't have to. But a simple electric inline valve on the fuel line feeding the lift pump would be standalone, easy to install and not expensive. Quick search found 1/2" valves for $44.99. Under $100 for sure, all in with switch, wire, fuse, etc.