I'm pretty sure the hot start/oil issue is related to some of the O-rings, etc. under the valve covers. It could be that's also what's causing my dead injector.
I've spent the day thinking about what the shops I talked to this morning told me, and also thinking about the advice here from Craig and SaltH2OHokie. The diesel shops I talk to are pretty clearly in the business of high performance PowerStrokes and want to sell you a built up $14k engine with head studs. They're not interested in the cheap fixes, whatever those may be. One thing the one guy also said was that, given the description of my blow-by (the oil filler cap doesn't shoot off, it basically just sits there and blow-by puffs out at idle), he thinks I likely don't have a physically dead cylinder. His words were "I've raced engines with worse than that." He also said that if the engine is stock, it really is pretty rare to have it actually lose a cylinder unless the injector starts dumping fuel in and burns the piston/rings up. I do still think I have one that's worse than the others, but if I can make all 8 run, that's good enough for me.
The other clue that came to mind was the other day after putting the truck back together following the IPR and ICP. The first time I did it, the #8 cylinder was dead (I think #2 was dead as well), and after fiddling with the connectors on the back of the FICM, I got #8 to kick back on. The connectors on this truck aren't in the best of shape, so it is certainly possible that there's a harness/connector/wiring issue causing it, and the buzz test makes sense.
I don't have the tool that can do the buzz test, but I'm thinking of taking it to the Ford dealer. They have a $100 diagnostic charge and I'll specify that I want the buzz test done among whatever else they do. If I have them repair whatever's broken, the $100 diagnostic charge goes towards the repair. I'm thinking they might be more pragmatic than diesel shops who don't understand why I don't want a 700 HP engine in my truck. Normally I'd tackle this myself, but I have enough other stuff to work on and while this may not be that tough of a job, I'm just at a point where I'd rather pay someone to do it if it's required.