1990 F150 sticking starter

Hello all.
I have a weird one here. I have a 1990 Ford F150 4.9 5speed that was sitting for a while. I drove it for a couple weeks but the starter kept sticking, and it would keep going after I took the key out. I could get it to stop after messing with the key for a bit.
Recently, it stuck as I was leaving my friend's house, and it would not stop. I had to disconnect the battery cable. It had been going probably more than a minute.
When I came back the next day, there was no power in the cab, no dome light, the key does nothing, no buzzing, nothing. Even while getting a jump, no power. I replaced the solenoid since it had been smoking from going so long. I jumped the terminals on the starter solenoid and the starter turns over fine.
I don't have much knowledge of vehicle electronics, it confuses me. Possibly I connected something wrong, but I would assume that something burned out to make everything stop getting power. One 30 amp fuse under the dash is melted, although it still seems to have a connection in the middle. The fuse box melted slightly with the fuse. I haven't had the truck long so it may have already been like that. The guy who sold it to me was a real idiot. Any help would be appreciated. Thank you all

Given the age of that truck, I'd probably start looking for burned fusible links. They'll likely to be ahead of the fuse box, closer to the battery. The links will look somewhat like wires, but will bend over too easily if they're burnt.

A quick survey of the fuses in the box would be a good idea, too. With the key on, use a test light or DMM and verify you have power at most of the fuses, and also have power on both sides of the fuse. That'll show if those fuses are getting powered, and if they're blown or not.

While you're looking around, double check your connections at the starter relay and the battery. Nothing fancy, just make sure they're right and reasonably clean.