‘75 Dart Sport Charging system issue(s)

Update: I’m a moron and somehow overlooked the super obvious alternator terminal stud that is clearly plugged into a black cap/connector near the top. There’s a smaller posterior terminal stud at the bottom (that I mistakenly thought was the main terminal stud) with no wires connected...

Current status: Battery not receiving charge. Starting to think there’s trouble in between the alternator and battery. I probed the alternator stud (while engine warm) and readings were way high 18.5+ V. Reading at battery (while running) is less than 12.5V.

First pic is alternator reading. 2nd battery while running.