Alright folks, it lives! Here's the update for posterity's sake in case anyone happens to be in a similar situation and is looking for insight.

Car sat for about a year until a 300D naturally aspirated showed up on craigslist for parting out. I pulled the injection pump for 100 bucks (sure beat the 1,500 price tag of a pump rebuild). After timing the IP with the drip method, I got the engine to fire up, but only after 30-40 seconds of cranking (not great). Once running there was a distinct misfire and lots of smoke, even after warming up. I put about 2 liters of H20 down the intake (a small trickle of water at high rpms) to no avail. Lots of steam but still misfired and still smoked. So, I decided to send in my injectors to https://dieselfuelinjector.guru/ just to make sure there were absolutely no issues with the fuel system at this point (I had already cleaned the fuel tank and replaced the filter at the bottom of the tank). Mark, the injector guru, said that the nozzles were cheap and one was totally frozen (probably causing the misfire). He installed used german nozzles that were in good condition and balanced the injectors. After getting the rebuilt injectors back, I installed a clear hose from the filter to the IP to be able to check for air intrusion. Purged the hardlines, ran my glow plugs for 30 seconds (they are on a push button with a burly ignition solenoid), and the damn thing started right up, even in cold weather (SLC, UT) without the block heater. It is firing up after 1-2 seconds of cranking, just like it should! However, the exhaust was still smoking. I decided to give the water injection another try now that I had a solid fuel system. After running 2 liters of water down the intake (again), the smoke is almost entirely gone. Most of the smoke cleared up after the first liter but I did another just for good measure.

Also, I didn't know the condition of the original IP or cylinder compression #s when I bought the car. It's possible a lot of the damage was already done before I twin-tanked the car, as the stock tank when I purchased ended up having WVO right in it and sat for 5-7 years. I drove about 300 miles like this before I realized what was happening. The strainer under the tank was totally blocking fuel and I found 1" of rusty oily sludge at the bottom of the tank. Perhaps those miles caused some of the damage to the fuel system.

So the lessons I've learned are:

- if your engine has minimum to low compression (one cylinder was reading 180psi!), it absolutely must have a strong IP and good injectors, but it absolutely can start right up. If its not starting right up, there are other issues besides low compression.
- water injection to decarbonize the combustion chamber resulted in much less smoke out the tailpipe. Installing a system to be able to do water injection periodically on the fly as noted in previous posts is probably a good idea, especially in a WVO or WMO system that could accumulate unburnt fuel deposits if the injectors are wearing. This can happen even with religious purge times and no fuel mixing.
- cranking no-start- my first response to this was to refresh the charging/starting circuit with new grounds, heavy gauge power wires, and replace the starter. This was probably wholly unnecessary as my primary issue was fuel related.
- if you are running WVO or WMO and are starting to have longer cranking times, send your injectors in for a rebuild before they cause unburnt fuel residue to buildup in the combustion chamber and cause damage that will result in low compression.
- If you just bought the car and it had been sitting previously or had an unknown history, pull the fuel tank and clean it before soaking your fuel in a potentially dirty tank that can cause IP issues down the line. I had ignorantly assumed the fuel filters would clean out any impurities in the tank and keep the IP clean- this was not the case.
- This one is still a bit of a mystery for me as I hear much conflicting circumstantial evidence, but one potential conclusion to all this is that settling and filtering WVO is not enough. It must be dewatered somehow, and an onboard de-watering filter like my vormax was not enough. Like I said, hard to know though with so many variables like unknown engine history.

I am curious what my compression numbers are now after doing the water injection... If I do another WVO conversion I will likely do a compression test before the conversion to get a baseline reading.