I think you are over complicating a simple process.If you are making tubes as thick as it sounds with that much plastic I see no way for success.To bad you don't have a copy of my video,it would save me a whole bunch of one fingered typing.
First of all forget the one handle cutter for what you want to do,and start thinking,a cutter that kooks like a rolling pin that you might find in the kitchen,but without the wooden center section.This section would be replaced with the shaft,washers and blades.You will need two hands,and more important,equal pressure.To assemble the cutter you will need:
3/16 inch steel rod,cut to the width of the blade assembly plus about 4 inches,faucet washers to provide a good firm stop for the first and last washers,JB weld to set the wood handles of your choice,two 3/16 self threading nuts(Pal Nuts).Make sure your blades rotate freely,with no wobble.
I usually make about two dozen tubes per four onces.You can make them as thick as you want,by cooling and dipping multiple times.Make sure you lubricate the tubes in a baggie,or whatever ,using scent or worm oil,before cutting the tails.When I was making the ebook,I didn't use lub,when taking self movies,to protect the camera from smudges,and the tails were a lot harder to cut.
Did you try a softer plastic formula for the first dip???I don't under stand how the tubes got that stiff.
I plan on selling Bojon tail cutters in a week or so(depending on mat'l suppliers).I wish you luck.Let me know on your progess.If I can help,I will.