I always used to enjoy a cotter pin challenge (afterward, if successful).

You say that you tried pushing it (the bent part of the cotter) back. If you haven't already done so, try threading the nut part of the way on and giving it a sideways whack with a hammer to straighten the bent section. (If you can't get the bent section sufficiently straight, neither the cotter press nor the hammer and punch will work and you're probably doomed to drilling the pin out.)

Edit: as a last resort before drilling (and only if you've given up on the cotter press), try cutting off the threaded part of the cotter so that the remaining portion is flush with the crank surface and then using the hammer and punch.

If the cotter press doesn't work, it's still worth trying the hammer and punch approach (but don't leave the bike sitting on the floor while hammering; otherwise, the tires absorb a significant amount of the hammer force).

By the way, I always found that pointed punches were unsatisfactory for cotter pin removal: too small a contact point. A solid axle from a rear hub always worked better for me. (For maximum impact, it's best to leave the nut threaded on so that its upper surface is flush with the end of the cotter.)

Supporting the crank arm can help if you happen to have an appropriate small-inner-diameter pipe lying around.

However, since that can still result in a significant amount of the hammer force being absorbed elsewhere than at the end of the cotter pin, I always preferred the opposite approach: hanging the bike from the repair stand's clamp by the tip of the saddle nose so that the bike dangles freely.

Or, if you don't have a repair stand, do what I do and hang the bike from a hook in the ceiling using an inner tube. (It can help to position a couple of chairs against the wheels to keep the bike from swinging around.)

This approach might seem counter-intuitive, but you want to ensure that the absolute minimum amount of hammer force is being absorbed elsewhere than at the point of impact.