Congratulations on the most voluminous description of a problem EVER! GREAT JOB!! If everyone would do this, it surely would help those who are guessing what the problem might be. But you really do have quite a problem.
You can buy a basic scan tool that will read P codes (others too) for less than $20, and you definitely should have one. With all the money you've spent, this is a greatly useful tool, both now and in the future. Or borrow one if you know someone who has one.
I would build and install a (home made) lift pump and additional filter (after the tank, before the pump). Having a lift pump will solve (or as some refer to it, hide) numerous fuel system problems. This should cost less than $100 for the main components, pump, filter head, filter, diesel line, clamps, wiring. You probably have some of this around your place already. If you want a fancy factory built one with all the bells and whistles, you can do that after you get the engine running correctly.
I would suggest cleaning your MAF sensor if you haven't done so already. Double check all the pins on the ECM and wiring harness to make sure none are bent and that all make contact as best as you can tell. Look at your other wiring looms for any shorting/frayed wires.
You didn't mention any DTC codes so I will presume there are none. Correct? And you don't have any gauges that would display fuel pump desired and actual pressures, MAF and MAP readings, etc?? Did/canyou perform a compression test?
2008 2500HD LT CCLB/Ally. Line-X, B&W Companion, MaxLoader Springs, Edge Insight CTS, Kennedy Custom ECM
2009 Arctic Fox 5er, Silver Fox Edition 29-5T, 3.6 Onan LPG, SteadyFast Stabilizers