You don't have kickdown because you don't have enough TV at idle.
The plunger isn't supposed to rest in the full out position. You need to setup the TV cable so that the pivot is 1.125 away from the throttle centerline.
This will give you proper TV cable motion.
If you set the TV cable for full TV at WOT, and you have overactive kickdown or late shifts, you can then adjust it back off 1-2 clicks. You cannot adjust it any higher because the TV plunger will bottom out and you either get a bent TV bracket, or not ever get WOT.
There will be some tension on the cable at idle.
It sounds like you have a very stiff pressure regulator spring to attain the pressures you have at idle.
Where was the trans built and what shift kit installed?
The TV plunger also feeds TV oil back to the opposite side of the plunger to reduce pedal effort, maybe this has been modified too.