My kitty has megacolon

I am in the beginning of what will prob be a lifetime battle with megacolon. My buddy is 7ish, a big (18pd)male. He's my life and his misery is breaking my heart. In two weeks he's had an xray to diagnose, several enemas, sedation and manual clean out twice. He's been on lactulose since day one, and Psyllium's powder in his wet food(vet recommended). She also wants us to get Cisapride because he is not going at all. I have to order this today. My husband and I have been researching non stop which is how I found this site. I am so TERRIBLY confused. Vet highly recommends Royal Can in Fiber Response dry food. Its 42.00 for 7 lb, very expensive. Yes, as sad as it is to admit, money is def an issue. So we need to try to put our money to the best use! I keep reading posts on here that say "don't use high fiber", stay on wet food..lots of praise for Miralax, some say no Psyllium, some use pumpkin, on and on....How do we know what to try? And what overboard would be...its causing me so much stress! I just want him to go back to some kind of normalcy without vet trips every other day. Can some of you with the most years of experience with this awful illness please try to give me some specific guidelines of where to begin that's worked for you? I'm worried now that the Psyllium I'm giving is a bad idea,I plan to order the Cisapride today which I feel confident he needs for motility, but also read on here that some swear by Miralax instead?? Please,please help us.Vets are great, but not versed in treatments other than medical(versus herbal,etc)usually. But we also don't want to waste money going in the wrong direction. Thank you for any help weeding through all this information!

I don't have any experience with megacolon, but I've found several threads about it that may help, and hopefully someone will come along who has some experience with this.  

My kitty doesn't have megacolon but he is prone to constipation due to IBD.  I have talked to my vet about it since chronic constipation issues can lead to megacolon.  Some kitties do better with Miralax.  She also told me that often Megacolon kitties will do better without added fiber.  In fact she said they will do better if the diet is kept as free of fiber as possible.  I think that what works for a kitty is very unique to that cat.