Yes, please stop the live food for now. Prune puree is fine, as is the oil. Those should help. If you haven't massaged his tummy during a
bath, try that. Work your way down from the armpit to the vent, gently, but with purpose.
Bathe him twice a day. Try putting him in the
bath tub. Make the water a little warmer than usual, and make it deep enough for him to have to swim. Between the higher temp and the exercise, this is often successful. Please remember to stay with him during the
bath.
Please describe your set-up, especially lighting. He needs to get to basking so he can digest his food. Is he in his hide? If so, remove it to encourage him to bask. Have you checked temps? If so, what tool are you measuring with?