The manual said, that "the vacuum booster will be damaged if the
bleeding operation is performed with the engine off".
Regarding ABS troubleshooting: read pages 5A-26 and 5A-24 of manual. They might give you some tips on what to look for.
My ABS unit just died due to one of the solenoids failure, I disassembled half of electrical part but did not found anything to repair, so I bought replacement on e-bay (hope it works). Just in case, the ABS unit is interchangeble with Trooper.