Is your Milidon pump the cast aluminum or the billet aluminum one? Both of them now use three O rings on them to seal between the block and pump, are you using a gasket also? If so, don't
How much torque are you using on the four 3/8 inch pump retaining bolts?
The shaft broke for a valid reason, figuring out what caused it is the hard part, huh Dang Murphy anyways
Good luck, let us know what you find, that will help others in the future