Sam, If I read what you said correctly earlier, the oil consumption is significant over a short period of time. Now that you have the turbo off, take the turbo oil line off and put a pipe plug in the opening. You would then have basically an NA engine. You could drive it this way the short distance that you drove it before to check for oil consumption. Cover up the crankcase drain, and fab a temporary filter over the intake to run it. If you sucessfully run without major oil consumption, then your culprit is in your hands. If the oil is still disappearing, then it's not the turbo.
As for the rear seal idea, nada. That oil would pour out on the ground rather than fill the trans. I suspect your oil is either going on the ground, or out the exhaust, and only at certain speeds. Ditch the CDR and go with an RDT. You could then name your truck "Smokey".