First item: The lift pump pushes fuel into the IP's fuel chamber under, maybe, 20 PSI. When the feed hole aligns with the vertical slot (shutoff condition) this fuel flows through the feed hole, up the slot, and into the delivery chamber (space above the plunger). See #1 and #2 in the photo in post 36. Now, if you crack the nut at the bottom of the delivery valve, that breaks the seal between the IP and delivery valve allowing fuel to flow out (under the 20 PSI of the lift pump). But it takes a lot more than 20 psi to open the delivery valve so nothing will come out if you crack the nut on the top of the delivery valve (which connects the delivery valve to the pipe). And the IP plunger cannot develop higher pressure (like 2000 PSI) because the slot provides an open passage between the delivery chamber and the fuel chamber.
Second: I talked to Tony at length this afternoon and it turns out the "correct" workshop manual for our tractors (pages dated Nov 2004 and back cover dated 2005) shows the old (prior to s/n EC4400209) stop solenoid configuration. Newer manuals that show our SS configuration have transmission (and probably other) data is wrong for our tractors. So, there actually is no manual for our tractors that is right for the engine and transmission. The best option, IMO, is to use the 2004/2005 DK45S shop manual for everything except the engine fuel controls and use the EX 35/40/45/50 manual for the fuel controls. I might add that Tony said our machines are (at least in some ways) superior to later DK45S models (and several hundred pounds heavier) .
I also asked Tony about just removing the SS. He said the SS guide protrudes into the IP, which is why it is lose if the IP and manual stop lever are removed; but it should be secure if only the SS is removed. This agrees with the EX manual that says you can remove just the SS to check injection timing but to use care not to lose the guide if you remove the IP.