But the issue is: How can a blocked breather force oil out of the exhaust? There are only two possible routes into the exhaust to my knowledge. Either it enters the combustion chamber via the intake manifold or around the valve stems or piston rings, or, it enters after the combustion process through the turbo seals.

I seriously doubt that bad turbo seals could pump that much oil past them. This leaves the sole option being direct migration into the combustion chamber. How could that possibly have happened? I don't think that much oil could get by the rings and valve seals in that short a time.
This pushes me to the conclusion that it had to enter via the bypass tube. Could the baffle in the valve cover have a problem resulting in the oil getting vacuumed into the bypass tube?

Can anyone else come up with an alternative hypothesis? I may be misled by the fact that I've had this happen before on a gasser.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13