Slow down Steve. The only problem you have stated is that you have to rev to get charge. I guess you know that from looking at ammeter. Not sure. You don't say that you have checked battery voltage during motor running and after a drive with motor off. You don't say you have a starting problem. So no real problem on your initial post.

Then you say radio goes off and on. Brake lights go off and on. Don't know how you know the brake lights are doing that?
Without wondering how the regulator works and understanding the circuit, can you tell us what specific problem you wish to fix?
You say you don't want to be a parts changer, then you say you are getting a new harness. THAT is a BIG part to change without letting us know exactly what you are trying to fix.
As I said, MAKE SURE your battery is good before doing anything else. Have it tested by someone who knows how to load test. You can just test the voltage yourself. Do those things and report back.

You need to know if battery is good/charged to 12.6V/being charged at ~14V.......by using a multimeter. Report results. One step at a time. The wonky stuff points to low battery. Battery going bad. Your tests will tell us if it's the battery or the charging system. But we don't know what the IT is. Where's the beef?

Jerry (Hotrod Lincoln) can fill you in on how the regulator works if that's what you want.

Right is right, even if everyone is against it, and wrong is wrong, even if everyone is for it. - William Penn