That is a made in Japan Charvel Model series guitar. The Fort Worth, USA neckplate was confusing to say the least and many people believed they had USA Charvels when they had these guitars.
I am pretty sure what we are looking at is what was called the Charvel Model 2. It was originally a single humbucker guitar and it looks like someone added the neck humbucker as it's placement doesn't look quite stock. They also added the mini toggle to switch pickups. There was also a Charvel Model 3a that was available with two humbuckers like this one, but the neck humbucker was closer to the neck and it had a typical 3 way, blade switch in a different spot.
These are decent guitars but no where near as well made of guitars as the USA Charvels that came before them. The most recent one of these I sold was a Model 1 in mint condition and it went for in the high $300's.
The Kahler trem on this guitar you have here is pretty horrible. You might be able to source parts for it through Kahler USA as they are back in business. Otherwise, I would take the nut with you to a specialty hardware store and see if you can figure something out. I always go to a store that specializes in fasteners for race cars and other specialty pieces and I can find most hardware I am looking for there.
I hope this helps. I wouldn't bet my life on this info as I was never really into the Model series Charvels. They are decent to good guitars and the higher the Model series number was, the more expensive they were. The Model 5 and Model 6 were neck through body guitars that were very similar to the Jackson Soloists.