I had a similar problem last summer, got towed to a dealer in the middle of nowhere iowa. They really didn't have any diesel specialists there and ford has a tsb that directs the mechanics to replace both the icp and the hpop in that situation. So I payed the $2700 and had them both done, because I was stuck and had no tools with me.
Now, after doing some research and hearing what everyone else says that had work done on their 6.0's and truly know the engine I would have taken a different approach.
First- I would have made damn sure I had enough oil in the engine, as little as 2 quarts low can cause a no start. I checked it, but maybe not as carefully as I should have. (I am sure your dealer checked that first thing, before they hooked up the diagnostic, right?LOL)
Second- I would have authorized the dealer to do the icp reg and sensor only. This is the more common problem, and with parts an labor it is only about $500.
Third- If that did not take care of it, I would have let them do the hpop. The hpop is in the valley of the engine, underneath the intake manifold. Huge job! 7 hours labor plus over 700 for the pump. At $150/ hour that is the piggy bank breaker. Either way they are going to charge full book labor for both jobs, even though they kind of work into the same job. So why not do the less expensive easy one first, right?
I guess it is possible if the oil is bypassing the bad injector, that COULD be the problem as well, but I would say more likely one of the first 3.
Hope this helps, I know autoenginuity is a good scanner, but if the sensor or reg is bad, it could be an inaccurate reading. I think the theoretic pressure to crack over the injector is around 400psi.