Holy Jesus.
This guy is cranking a 120watt amp at practice? Sometimes 2? Are you for real? I didn't play much after high school, picked my bass up again 3 years ago, been playing with bands now for 2 years. In my first search for a band, I got really lucky. Went to audition. I could hear these guys out at the street (they practice in a basement). I brought a Fender Rumble 350 combo, which I normally can only turn to 2 at home. At 3, it interferes with the family tv and at 5 it shakes windows and doors. The guitarists were playing through 100 watt heads, I don't know how much they were turned up, but I had my rumble cranked to 10 and could barely hear myself. I didn't know any better, and was disappointed that I didn't get the spot. A few months more experience, I count myself lucky I didn't get it. In my current bands, we can still get a bit too loud at practice, but we try to keep it manageable and don't complain when asked to turn down. We're definitely amateurs but have professional attitudes.
Most of the time, a 40 watt head is all the guitarist needs, especially at practice. If they are mic'ing the guitar or going DI (using the amp for stage sound) a 25 watt head will do. And will result in a much better mix, as long as you have a competent sound tech. "My tone", they say, "my Marshall!". I say, save your tone for the record, practice is about getting the arrangements down. The show is about entertaining and selling drinks. If the staff can't hear to take orders and the audience can't talk with each other....
I also missed the part when you said you started the band. I'd say it's band meeting time. The options are: we turn down, the guitarist goes, or I go.