I agree that 60 LMB of 5"-7" is not too many for a .75 acre pond. In fact I would say it is just about right, maybe a tad on the light side...
I too am baffled why the growth of your LMB is so slow. As Theo said, adding more FHM is just a VERY expensive feeding regime. It's hard enough to establish FHM before stocking bass and about impossible after you have stocked them.
A couple other questions for you:
Is there aquatic vegetation in the pond? Species, % of pond covered?
Substrate the pond is made out of? Mud, clay, sand etc?
Have you done a seine survey of your pond, if so what were the results?
