1987 Toyota Celica Alternator or otherwise?

My car is a Toyota Celica 87 with under 60K miles. Recently had the clutch replaced after it sat for a couple month while I rounded up the money and parts and people necessary =( Just got it back a month or so ago and it was doing great.
Then I stopped in to get some gas, and it wouldn't start up, tried to push start, nope. Jumped and let charge for a little (under 5 minutes, lady had to get going) and I drove about a quarter mile before it died again as I was driving. So I took the alternator and battery to autozone to have it tested, battery passed, alternator passed. Put both back in and cleaned the ground cable for the battery, starts up fine?
I'm fine with that. Then got retested and while the car was off, it was using about.8 amps after testing for a while. When it started about.2 I found a trunk light that had been stuck on, unsure of the draw now.
Before I found that light I had to disconnect the battery when leaving my car somewhere so i'd be able to drive away.

But still it shows on my dash that the power in the battery is near 18, at the very top of the meter. When it should be near 14?

As well the copper wires within my alternator have now turned a metallic blackish color vs the copper gold they were before, some of the wires down deeper appearing a reddish color.

As well there was one instance where I stopped and peeked under the hood and the the alternator was very hot, some of the electrical tape that was wrapped around the (ground maybe?)Had melted off. It drives and starts just fine though?

What could be wrong? I figure something involving the alternator, yet it was tested to be fine. I want to take it down to be tested again.

Thanks a lot, JOEL