65 Barracuda daily driver

The car was sitting for like two days and then wouldn't start and only cranking slowly. So I took battery and alternator to the parts store and had them tested. Battery was bad, but alternator was ok. Luckily they gave me a new battery for free. This is like the 3rd battery they gave me under warranty in the last 8 months or so! But that's possibly how all of that started: In October the car wouldn't crank or start at all, so I took battery and alternator to the store and they both tested bad. Got a new battery and a 65 amp alternator instead of the 60 amp alternator that I had before, because that's all they had. I don't even think any more that the higher output alternator was really the issue. Anyways, at some point the battery went bad again and I got a new one. A couple of weeks ago when I was checking voltages with a multimeter I noticed that the battery was charging 17-18 volts. I had another old voltage regulator laying around, so I installed that one. Now it was charging 14-15 volts, which I guess is a bit better, but either it was already too late for that battery or that voltage regulator was a bit better, but essentially also defective. I assume that already in October the voltage regulator was bad and was responsible for the death of the alternator and the batteries?! I assume the battery was overcharging/ boiling and that's why it got worse when it was hot?! Anyways, I also ordered a brand new voltage regulator and fingers crossed that will be the end of those issues!!!