Alternator...

No way for me to know. I am GUESSING you have a Delco "one wire" which does not use a field. So leave the green alone. Do NOT ground it as it may still be connected to the original VR

The charge voltage is a "bit" low. Did you measure running / charging voltage both at the battery AND at the alternator stud? This will show if there is voltage drop. Measure with engine running at RPM to simulate low to medium cruise

Measure with lights, etc off, and again with lights, heater, whatever loads you have turned on. If there is a "sag" between the two voltages, you have too much drop in the alternator circuit.