2006 Chevy Impala dying while driving

I have a 2006 Chevy Impala LS (flex fuel) while I’m driving the dashboard sends off a warning of “reduced engine power” as my car loses power and I lose the ability to use my gas pedal. Meaning that it no longer has friction and all I can do is press on it and it’s just as useful as Face slapping the air.

What I have found is that a prior existing issue was that my passenger side taillight would not work most of the time. The rear lighting in total would flicker while driving. Someone had told me the brake light would just go nuts, but never elaborated. No matter if I was or wasn’t using it. It just goes.

Currently while I’m driving with and without the headlights on the car will send off the warning. Cold or warm weather doesn’t matter. This will especially go off when I turn on the radio, AC & use the defroster. A fuse for the Day time headlight was burnt out and replaced. Yes it’s working thanks. New battery and terminals were installed and the alternator passed flawlessly. With a fuse test light some of the fuses under the hood will or won’t light up. A fuse titled as batter #2 one entry will light up happily but the opposite is more of a shy dim. Fuse box on the interior fuse for the trunk (not the trunk regulator fuse) is not turning on it has been replaced but still SOL. I was told the trunk fuse would not set off the warning/ issue.

The only way I can have the engine moving is if I diddle with the main power terminals. it still turns over even if the issue wasn’t cleared off.

I don’t know how to approach my issue without having to turn it into a car electrician with $ I don’t have to spend.