DK,
Well you got the leak fixed. Congrats!
Is that the woodruff key for the pulley? If it is, you have gotten it jammed. Gently tap back the sprocket to free the front woodruff key. Be extra careful not to hit the crank.
If you can find a piece of pipe to fit over the crank, and fit against the sprocket, it would be better. That way you apply even pressure on the sprocket. Then remove the key. The sprocket should come off.
When you're done, and ready to assemble the sprocket and pulley, make sure the crank is clean of any corrosion (RUST). Then clean the inner surface of the crank and sprocket.
Apply a light coat of grease to the inner surface of the sprocket, the pulley, and the crankshaft and woodruff keys to prevent corrosion.
Examine the keys for any signs of hairline fractures, cracks, or breakdown of the metal from stress. If they look good, then reuse them. If you have any doubts, replace them.
You could stop at a machine shop and have someone look at them. Someone who works with metal. The one in the picture looks pretty good, but with out a close examination it is hard to tell. If they are not corroded, and there is not chips of metal flaking off of them, they are most likely OK.
Keep in mind these keys take a whole lot of stress from the torque of the motor.
There is NO WAY you bent the crankshaft. But, if you continue to try to pull the sprocket with the key jammed, you will split the sprocket. Been there, done that!
You're doing good so far. Keep it up, and hang in there. rangerj