You MUST MUST MUST isolate the charge line from your alternator from the rest of your electrical system except where it runs back to the battery.

As long as the alternator is turning, it will power up everything in the car when run back to the starter solenoid lug. Throw the switch to kill power from battery to solenoid, you still have power feeding from the alternator.

Think of it like your on/off is a dam. The battery and alternator have to be on one side, and basically the rest of your stuff on the other side.

Now if you wish to wire it that way, you could put a relay in the line and have it trip when the on/off is thrown.

I've posted some diagrams before. I like to use relays for the starter line and alt line at/around the battery location.

Sounds like you are getting some advice that makes this a bunch more difficult.