It took two of us and hauling the frame down to the Walk N Roll shop, but I finally got those cotter pins out of my cranks and the bottom bracket mostly taken apart. The drive-side bearing cup is still corroded in place, waiting on another trip downtown to borrow another tool, and possibly a mallet, but I'm inside and starting to clean out the layer of dried crud. There's one glob of a substance resembling ear wax, but the rest of the grease is gone. Next step: new bearings and a lot of scrubbing with a wire brush and steel wool, which will be a lot easier and more effective if I can get that bearing cup off.
Anyway, what we ended up doing about the cotter pins was to press them back out with a vise, using a couple of large nuts taped together to make a hollow for the pins to be pressed out into.
