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...I don't think you'll have much luck riding it off. A cotter, stuck like you describe it, is seated in there well. All the nut does is keep it snugged down, and you've accomplished an alternative to that by bending it.
That said, drilling one out is not a big deal, just PIA, If you can, cut it off even with the crank arm at the threaded end, then center punch it to get a starting point for your drill, Choose a drill bit that is slightly smaller than the cotter itself, and drill it down far enough that you have a nice empty hole to seat a drift or pin punch with an end that is a litle smaller than the hole. Then drip in some ATF/acetone mix on both ends of the cotter, give it a chance to wick in there, and whale on the punch with the crank arm supported on something like a pipe or a notched 2X4 that is supported on a solid surface like a concrete floor. The pin itself is much softer than the the crank arm or the spindle, and you don't really need to go past the spindle intersection with the cotter anyway. Just be careful not to bugger up the hole in the crank arm, which is clearly visible.
I have done six or ten of them this way. LIke I said, PIA, but not all that difficult once you resign yourself to it as the solution.
As a bonus, you can turn the remains of the cotter into a lavalier or a keychain fob.
