1986 Fiero SE: V6 4 Speed.
So, my Fiero is developing a few electrical gremlins after 2 months as the 2nd owner. About 2 days ago, every interior dome and foot well light ceased to work except the passenger side light near the door. If I pressed any of the dome light buttons to activate them, or turned the interior light slider to max, oddly enough the passenger side light would turn on. Then on my drive home last night the light was flickering on and off randomly and then stayed on and wouldn't turn off no matter what. I unplugged it. The fuse to the Radio/Interior lights is intact but has a 25 fuse instead of a 20.

This may be unrelated but this morning I started the car, the idle was around 1800 RPM as it has been when it is really cold outside. Suddenly the check engine light came on and the RPMs went way down to like 800, normal once its warmed up. However, for the next 30 seconds the idle surged from 800 to 1500 RPM back and forth. Then it shot back up to 1800 RPM and continued warming up. The check engine light went away. The car warmed up normally and drove fine afterwards, it just hasn't happened before. Any help with these issues would be great.

Read ECM codes. Very likely have at lest one.
Engine high idle and MIL on can be ECM trying to make E power for iffy wiring, Alternator or battery.
Test volts at battery before during and after starting the car. Charge bat = 12.6v, engine running should be ~ 14.7v

pull lighter socket and disconnect it before replacing Bat fuse and maybe others w/ right fuse(s).
socket can rust or things fall into it causing problems. See my Cave, Lighter
If right fuse blows still have other problems maybe harder to find.

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Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)

The Ogre's Fiero Cave