The electric scavenge pump is AC with DC control. It's only a small pump and can take hours to shift fuel. Under automatic operation it stops after 2 hours.
During jettison, according to the Boeing schematics, the HST plumbing has a path directly to the Jettison manifold and to the Jettison Nozzles.
Rgds
NSEU
P.S. Again, I'm surprised you didn't ask these questions on the PMDG AVSIM forums. The people who created the simulator had input from professional pilots and engineers.