Makes it harder trying to get it started on three cylinders as well. We have the option of working for hours on cars ourselves.

It is sounding like you do have some compression. A working mechanic would waste no time seeing if it is enough. You want to know how your glow plugs are doing?

Rough way but better than none. In the dark you should see the squiggly wires glow somewhat that are between the plugs. They are resistance wires.

Many older diesels do not like to start with just one glow plug out. You are in an even worse situation. The one cylinder is not seeing any fuel. The only way it can right now is by feeding a fuel supply replacement through the induction system. As a real example here.

Engine tries to start by rotation and it hits a dead cylinder. That is why I suggested you carefully check to see if you can free up the bad injection pumps element if frozen. You will have to do this anyway at some point.

Sending that injection pump out for service would be expensive by the way.

Also if the block heater is still good. Using it to heat up the engine before trying to start might help. You never know if the valve maintanance for clearance was kept up over the years on any of these. At this point you do not need adjustment wrenches. Unless a quick valve clearance check reveals that you do not have some clearance on each valve.

Good job finding and fixing the fuel supply leaks by the way. You said you got it to run once. That is a really hopeful sign. It proved it can run even with all the current issues. That is enough to start dealing with it systematically.

Shot gunning just costs money and often that money spent gets you nothing in return. Get some penatrating oil on that third injection pump elements piston for a couple of days before trying to free it up. That and checking that the valves have some clearance would be my next steps.

Read up on the best approach to tap on that injection pump element or check to see if it is free. Chances of the element being stuck to me are a reasonable possibility. You are attempting to bypass a know fault and guessing at other things as well. You almost always address what you know is bad before moving on. It is both common sense and logical. We all can all make things harder than we need to at times. I have been there many times myself over the years.