That would better fit his symptoms wouldn't it? It's like he is getting too much vacuum at all times, which would pull the diaphragm and the pin back, making it shift early. The pin being missing would do the same thing wouldn't it? You would think a vacuum leak at the VRV would reduce the vacuum available at the modulator, making it shift hard and very late.
A quick way to determine this would be to pull the line off like I suggested and see how the tranny reacts.
Take a look back a ways on a thread I did on this very issue. I went through every scenario and ended up just adjusting the VRV "wrong". One good quick tip is removing and pluging teh line to the modulator.
If you then get very late harsh shifts, the trans it self is OK. The default if all mechanical parts are good is NO VACUUM=LATE SHIFTING. Since you have a hand pump, run a hose in the cab and you can do your own shift points. 0vac=late, 5 vac=maybe 2200 rpm 10=1800, not exactly but just an idea how it goes. Definitly should be a huge difference between 0 vac and 20 vac,if not problem is in the trans not vac system.
I finally tee's a gauge into line to modulator, and found I needed far less vac than VRV setting proceedure called for. Shifts about right with 7 to 10 in vac.