Hello, Balletbarre.
I'm sorry you are facing so many difficulties. Can you try Metamucil before your meals? It might help to bulk things up so that you can hold on. Liquid stool is difficult to hold, especially while asleep when your muscles are relaxed. Have you had an endoscopy to check for pouchitis? What does your old specialist say about help, if he says the pouch is not working due to radiation?
When you can't have a bowel movement while on the toilet unless you stand up and sit down again, try this: when you are on the toilet, lean backward slightly. For a few weeks after my reversal I had difficulty passing stool. I found that leaning back slightly, as if you were going to rest for a moment on the tank, and holding that position for a minute or so, worked every time. Just lean back a little bit, but DO NOT rest your weight against the toilet tank (don't push the tank off its pedestal --- or you'll have a whole new set of problems). Leaning back seems to straighten out the curve in the j pouch, and gravity hopefully will take over. I've also read that moving gently side to side while on the toilet can help "shift" the contents of your pouch and get it moving. (You can post new messages by clicking on the bright green banner at the top right of the page.)