dont most trucks have a torque converter test port on the control valve?
There should be ports for overall pump pressure, clutch pack pressure (fwd and reverse) , and torque converter and possibly even inching circuit pressure.
You'll need the service manual to tell you which ports are what and where they are.

I'd hook a guage to this and see what pressure your getting at idle versus when its rev'd up @ the torque converter port. This could reveal alot. You should be getting some kind of pressure at idle and that should increase as you rev up the engine. There is a minimum and max reading you should have.

Yes a torque converter can break and even wear out. This would explain no movement at idle as oppsosed to rev'ing up the engine and getting the jerk and then movement.