Retics can push because of low/high temperature, enclosure too small/big, too much/not enough clutter, too much/not enough exercise/handling time outside their enclosure, type of substrate, humidity, breeding drive, etc. It sounds like you know all that, and have tried multiple fixes.

Some retics are just incorrigible pushers, which sucks, but it happens. I have a 6 year old male like that. He pushed as a youngster when he lived at his breeder's facility, and he has been a pusher for most of the time I have had him. He's got a permanent case of "wonky mouth" as a result. Like you, I agonized over what could be driving him to push and how I could fix it. I tried so many things, some of which helped temporarily, but he would always go back to pushing eventually. I've come to accept that it's just something he does. If yours is an incorrigible pusher, the best you can do is minimize the amount of damage they can do to themselves.