Have you TRIED bigger prey???? From what you said you've only tried pinkies and hoppers.
I honestly want to help you here, I'm passionate about these animals and love helping people enjoy theirs.
But you're going to have to basically forget everything you know about feeding. Wherever you learned is a million percent wrong. So let's work together from scratch.
Oh, and PLEASE unplug your UTH until you get a THERMOSTAT.