Weird brakes

I'm envious that you can get out and work on the ride when the rest of the east and midwest are hacking out of ice. IMO, start with the easy stuff first. Since you say you replaced a rear wheel cylinder, is it possible that there is a little air in the line?

The best cure is to bleed the system. You'll be doing this with a new master cylinder. Keep fluid coming out of the bleeder valve until you have a clear stream with no bubbles. Check MC frequently as it is not good if a reservoir goes dry. Use this for sequence. RR-LR-RF-LF (work from farthest out towards master cylinder.)