I'm slowly coming back to the forum, but I've had two experiences with prolapse. One was Wilbur, and he, unfortunately, did not make it. He was only about 12 weeks old as well. I got up and was giving out hay before I left for class one morning, and he didn't come out of his house. He was in with Twilight and Fluffernut then, and there were bloody spots on the ledges and bedding. By the time I found him, the prolapse was too bad. We made it to the vet, and they applied three sutures, but he died a few hours later.
The second prolapse was a survival story. That was Rocco, one of the first rescues I ever took in. The family that he was with had run out of food and he had only had little scraps of hay cubes, cheerios, and catch this- dog food. They just kind of assumed that he was like a wild rodent and could survive on anything. So when I got him, I introduced pellets and fresh hay right away. We don't know what started the prolapse, but I woke up and there was a trail of bloody diarrhea leading into his house, and he had about an inch of intestines hanging out. Rushed to the vet, and she used a stitch to hold them in place. He was on injectable baytril, metacam, and critical care every 3-4 hours. About six hours later, the stitch broke and they came back out. I used a little vaseline and managed to get them back in, then were back at the vet's at 8am. She gave me a cream (I can't remember now what it was) to apply to the area and to use to remoisturize in case them came back out again.
Luckily they stayed in, but, like King, Rocco did not poop in the first 24 hours. Did some xrays and there was a little gas, but his gut was moving. So we started simethicone and continued with the antibiotics and pain meds. Twelve hours later, still no poop, but he hadn't been drinking enough, so we started forcing fluids and did some IV fluids. 24 hours after that, still no poop. His gut was still moving and there was no gas, it just wasn't coming out. We did more xrays to make sure that his intestines had not gotten tangled, and everything appeared fine. At this point we were at about 3 1/2 days of no poo. We started motility drugs, and still no poo. He still appeared dehydrated, so we changed the bedding in his cage to white fleece so that I could make sure that he was urinating. I started to make the critical care more watered down and fed more often. About 5 days AFTER all of this started, we finally had our first poo!! I was never so excited to see poo in all my life. What my vet finally figured out was, after the prolapse, the intestines were not staying properly hydrated because he was not taking in enough fluid. Once we really got him hydrated, everything started to move. I continued the critical care around the clock for another week, then slowly started to make the mixture thicker and allow him to eat it off of a spoon. About two weeks after his first poo, I reintroduced a little bit of pellets into his diet, and slowly switched him back. He was back eating pellets and hay again about two months after all of it started.
It was a long, hard, fighting road, but Rocco made it! Make sure that you're keeping King really hydrated, his belly full, and his gut gas-less. What I did for some cases of severe GI stasis was to hold a heating pad on its lowest setting on the gut area of the chin. It might aid in moving things, but REALLY be sure that you aren't keeping it on for too long. I hope that this experience might help you...keep doing everything you already are, and we have some paws crossed for poo soon!!