You could try emailing a company called Mars Keel and see if they have any suggestions. I would hesitate before cutting out the lead on one side of the keel bolts. It's going to be very difficult to get anything to adhere properly to the lead. Things may stick for a little while, but all of the expoxies will have different expansion rates than the metal, hence you are going to end up with separation at some point, and the keel may well just fall off.
If you have cracks, I would be tempted to try drilling holes and inserting bolts to hold the pieces together securely, and then filling in the holes with something to fair the keel.