Tried to read the above a few times, but still not sure what the main question is.

In general terms, external BB's never run as smoothly as internal/cartridge BB's if move by hand, when pedalling, this isn't noticeable.

With FSA MegaExo BB's, if in doubt, just replace with a Shimano HT2, they are compatible, and Shimano should be easier to find. The compatibility issue that you seem to be having is with the crank, not the BB, have you checked the techdocs to ensure you are assembling in the correct order? FSA Technical Information - FSA