As a Ford employee, please accept my most sincere apologies. This is the kind of crap that is killing Ford Motor Company. I too have had some horrendous experiences with Ford dealerships (two of them to be exact). The dealerships are not part of Ford, but rather a sort of franchise run by independent owners. They should still be held accountable by Ford Motor Co., and the particular people who you have been dealing with should be publicly hanged in front of all other dealership owners/employees.
Has anyone checked the turbocharger itself? I don't remember seeing it in your post, but the 6.0 has a variable vane turbocharger. If the vanes are not adjusting correctly, this could cause the low power/stall issues that you describe.....
This may be a longshot, but do you have any international truck service centers in your area? You may try calling them since the PSD is an international engine. I don't know if they can do anything at all for you, and I have no idea how that works with Ford's warranty but it sounds like you have done everything else.
Or, you may very well have a lemon law case. I'm not sure how that works but I'd be finding out if I were you!
Good Luck.....