I have never had an issue bleeding a line, even an extended one.
I guess my next step is taking the rear caliper apart.
The master cylinder is put together right. Something must be blocking the flow in the caliper itself.
It seems like it's sucking, but there's no way it can be..
Bleeding the rear brake line is about a 3 minute process with a Mityvac. If you don't have one, I suggest spending $40 and getting one.