Every thing that you have written sounds right. I would change the paper you are currently using to a uncoated stock.
I have seen night and day difference from using a coated stock to a uncoated stock, especially with xerox.
a couple of extra tips are to slow the machine down, try running the machine with no fans, thicker gauge film with more adhesive than the polyester, try another digital film from another manufacture, increase nip pressure, sell your printer.