Experince with B&M 50442 - B&M Tork Master Converter

Any metal (steel or bronze) or clutch like material in the oil? If the converter is going away, it could be the one-way (sprag) roller clutch, the vanes on the converter pump coming loose, bronze(brass) from any brazing that may have come off the pump vanes, cluch like material from the fibre washer in the converter, used by some instead of bearings to support the inards of the unit, and if there is a bearing used, the bearing itself coming apart. The sad part is if the converter is coming apart, there isn't anything you personally can do to repair it.
Drop the pan and check for junk in the pan/filter. If it's clean,pull the transmission and converter out, if you've eliminated all other possible causes for the lack of power. Tip the converter over and drain the oil see if any junk falls out.
I feel for you.