Hi all, thanks for the responses.
I've bled them (of course). They all run free of bubbles (Except the one with the leaking cylinder), but the front brakes still have old rusty fluid in them, so I should probably flush them.
I do have the dual cylinder (thank goodness), so it wasn't hard or expensive to replace.
Bob, if your car has the dual-cylinder system, the master cylinder isn't too hard to find, and I have a part number for it.
Nicholas, I do mean foot to the floor. I don't think the pedal actually touches the floor, but it goes as far as the master cylinder will mechanically allow it.
I tried readjusting the brakes (front only) to be tighter (probably pretty close to 1 rev) and noticed that they drag unevenly. Is this normal? (I suspect the brake shoes are unevenly worn, since the brakes were (I think) pretty out-of-adjustment when I adjusted them. I do have sources for new shoes (I did a bunch of internet-sleuthing to
find them), but they're still $50 for a set of 4, so I'd like to try
working with the ones I have, first.
Of course, tightening the brakes didn't help any.
I think my next steps will be to flush the lines, maybe just by opening the bleeder on one at a time and letting the reservoir run down (I'll top it off now and then).
I might also order a new set of rubber seals for the rear cylinder that's leaking, and go through taking the axle out and working around it all over again...
For a long term solution, I think I'd like to somehow incorporate rudimentary regenerative or plug braking. Save expensive brake parts, and it would help the braking power of the car a lot.
(Fun fact: If you have a contactor-based system, you're all set up for regenerative braking already. Just stick it in reverse while driving forwards, and apply the accelerator lightly! It worked for me, but I don't think the BMSs on my Li-ion batteries liked it a lot... Don't actually try this, since it's terribly uncontrolled and probably bad for your batteries.)