[john70t]

1. You are getting 13.5v to the window connector, and this changes from 0v to 13.5v when the dash switch is closed?
(If so, it is upstream so the fuse and circuit up to there is good.)

2. The heating element lines on the window have full ohms/resistance, and thus continuity.
(this will change with higher loads. a wire with one strand left will show continuity.)

3. But the element circuit is not heating up.
(amps not flowing through it)

I would suspect the return ground to the fuse bus, or a ground wire got broken somewhere hidden, or maybe there is a relay on the ground leg.