The ballast resister does not use a ground. It bolts to the firewall but all the current flows from one terminal to the other and only effects the ignition system.
There are a number of issues you have identified.
Charge indicator going all the way to the right.
Alternator belt / tention
Voltage of battery / alternator
Charge indicator, typically the indicator will show charge to about the first right tick after starting, then within a few minutes if driving will settle in around the center. If the battery is drained it will stay to the right a long time ( I had drained my 67 dart battery till it would not start the car. Jumped it and drove it for about 30 minutes. The charge indicator stayed to the right the entire time. I ended up putting the battery on a charger over night, next day back to normal) try putting the batt on a charger over night, auto parts store can do it for you if you bring the battery to the store. There is a possibility the battery is failing and taking more current to charge then normal.
Your belt might be too small, or the adjusting bar is in the wrong hole. On my 273 the adjusting bar does not need to move only the bolt that goes through it and to the alternator needs to be loosened and the pivot bolt loosened a tad to adjust the alternator. The alternator should sit midway through the adjuster travel slot
Your engine off battery voltage seem about right at 12.75 ish. Your engine running battery voltage at about 13.5 is ok too assuming the battery is not fully charged.
67dart273 asked a bunch of questions that need answering.
I am making assumptions here that your car is stock and no added loads.