I would concentrate on the humidity. I had a similar issue but my set up is a glass tank. I was using paper towels and having trouble keeping the humidity above 50%. First shed was horrible and I spent an hour soaking Dusty and working off the left over shed. This including having Dusty dump a giant poop all over me! I changed to Reptile Prime dampened and the humidity is now in the 60's. I have kicked it up a bit when he blued up. Yesterday I was greeted with one nice long perfect shed.
Bill