The problem of playing during reroll is because the stack suction
supply is not being turned off when the lever is moved.  You may have
installed the suction box after this control, or it may be a linkage
problem.  I'm sure many people more familiar with your stack can assist
with that problem.

In regard to the foot pump having no resistance, if it worked previous
to the electrification, then I'd bet your suction box has no check
valve.  You can easily test for this problem by blocking the hose to
the suction box, and see if the foot pump returns to normal operation.
I had this very same problem with a suction box that was added to my
piano years ago.

Michael Hamilton