Smaller master cylinder. That will get you going until you're ready to do some upgrades.
Take care of those lines like the others suggested.

If the pedal isn't spongy there is no reason to bleed the rears.

If you do need to bleed upside down calipers it's easier than you think.
Open the master cylinder cap.
Unbolt the caliper from the axle.
Hold the caliper at a funky angle so the bleeder is the highest point.
Open the bleed screw and let it gravity bleed for a few seconds.
Reinstall.

I had to do that on my TSM rear brake calipers.