After sitting for about 2 years, I've finally installed my carpet kit and was burning the holes (the solder iron tip worked great) in it for all the seat belts and seats. As I begain putting in the seatbelt on the driver side tunnel, I noticed that it was binding up. I cleaned the threads and the bolt and tried it again but it was still binding up. Long story longer, I figured out that a thread had partially broken on the bolt and had probably gaulled the threads and got crossthreaded in. Eventually after several hours of working on this I began to say "f*ck it" and tightened the problem bolt all the way down.

Currently all the bolts are in and are very tight however, should I be concerned about the integrity of that seatbelt bolt thread? Even though it went on and was very difficult to screw on but is now very tight and seems stable, could this be a problem for me in a bad accident? How do I go about fixing it if so? Weld up the hole and rethread? Go to a bigger size bolt?

Leave it like that, IMO, other parts of the seat belt assembly will give up before that bolt.