To warm up properly, take adequate rest time, etc then usually an hour is sufficient for two major lifts. For a very early novice, you can get 3 barbell lifts in in an hour. But once you get stronger and add warm up sets and more rest, 2 starts to hit that 60 min ceiling.
I've probably just put the Press/Bench on the AB rotation, Squat on Monday and Friday, and Deadlift on Wednesday.
Probably, although not critical on exercise order. I have one guy that does this set up and prefers to deadlift first, before pressing. Most prefer to keep it last. On volume, yes, likely the same.
Yeah, but the light squat really isn't the culprit for eating up time. That comes from the volume day.