I just thought of that. If I have room in my box for two double pole
breakers, I'll try to do alternating circuits for both branches. I
think I only have 3 slots left so maybe I'll do one double pole and one
single pole.

I do have electrical service in my garage and it's at about 125'. I
believe it's a 14GA 15A circuit. I know there's a voltage drop issue
there because I can't run my little pancake air compressor there (it
will barely kick over and never actually run) but the compressor runs
fine when run off an existing outlet right by my circuit breaker (for
the sump pump).

I have a bunch of 15A breakers in my box for my house. Is there any
way to make more room in my circuit breaker box for additional breakers
or is the only solution to upgrade to a bigger box (which I have no
plan on doing)?