I have the same thing and bought a helicoil kit to fix/re-thread the nut, once I pull the bolt back out. I bought a new seatbelt and it comes with a new bolt. I think these are fairly standard and you can easily pull one at the junkyard. Dunno that running a die will get you enough useful thread on that bolt. I have extra bolts, but am sure that the nut is where my issue is going to be worse.
By the time I send ya a bolt, U coulda already got one from another Toyota at the junkyard. If you find that the nut is jacked up, LMK and I'll send you the helicoil kit (it has the tap) once I've done mine (don't go spending another $50 for the kit). Comes with 6 inserts and I'm only using 1...
Good luck!