i to agree with Dave. i recently was blessed with a failing balancer found upon inspection thats done everytime i change the oil. im 1 of those that are nearly considered to have ocd when it comes to mechanics. so needless to say i went all out and did a retarded level of research before i went forth with replacing the balancer.
in my research i found these things have a very very tight tolerance that must be adhered to. the bore of the damper requires a .001 to .0015 press fit. if its to loose it could cause the damper to move and damage the key way and or the retaining bolt.
if its to tight it could cause the damper to gall and weld itself to the crank. (these are not my opinions these are the facts)
since yours is braking the retaining bolts that would stand to say your balancer is to loose and needs rebuild/replaced. you could have it rebuilt as they would refill the bore and hone it, however after the cost of this process you would be better off getting a new 1. the cost will be about the same. scp, ford, midnight auto, and im sure even Dave Dalke would have the proper retaining bolts for the damper. im not sure but i would almost bet on it that dave can get you a new balancer. if not then scp has the bhj balancer. autozone also has the stock balancers (new) but if i recall its like $40 or so and you can have the better bhj.
when installing the (NEW) retainer bolt ensure its torqued down to a minimum of 103ftlbs up to 132ftlbs. the bolts for the crank pulley should be torqued to 20-28ftlbs. in order to torque the retainer bolt properly your going to have to restrain the crank pulley in order to apply enough torque. this will not happen without restraining the movement of the crank. i got mine as tight as i could before i started to turn the engine then installed the belt and had a helper use a strap wrench on the water pump pulley to hold everything still. it worked like a charm.
i hope this helps, good luck.