The way I switch from live to frozen is this.
Once they are eating consistently (which yours is), I get a f/t rat fuzzie or pup and thaw it out with a mouse in the same ziplock back. Once they are thawed, I heat them up in the same bag together. When I go to feed, I hold the rat with the tongs by the neck, so that it's being held as if it's alive and crawling towards the snake. Usually, once they catch the scent on the mouse, they don't hesitate. I've had pretty good success with this. Good luck!