I bet I know exactly what the problem is, I've seen this before. That mouse nest is the source of your problem. When you remove the pressure plate you'll find it's stuck in the disengaged position.
When you started the engine, the nesting materials spun out from center and packed in around the fingers of the pressure plate. Every time you pressed the clutch it compressed the fingers and allowed more mouse fodder to pack in and prevent the pressure plate from re-engaging the clutch. Press the clutch in and rev the engine and you've compounded the problem.
At this point the only thing you can do is replace the pressure plate. You wont be able to sufficiently clean the nesting out for the pressure plate to work properly.
This happened to my 3600 last fall, i changed the disc and bearing, took the diaphragm p-plate apart (3 small bolts) and cleaned the exploded mouse condo out of it using a hook dental pick and compressed air. Real pia, but worked fine after deglaze of p-plate and flywheel. It don't chatter, buck and jump like it use to. Its a smooth shifter. Good luck with ur project.
btw, i had both pieces of the cover assembly installed prior to construction of the condo. they must enter thru the timing hole.
