I'm so sorry this happened to you and your boy, and haven't read all of the replies but I'll share our experience. My Sophie developed bad IBD at about a year old. She was very sick and we worked with a holistic vet for four years who had me home cooking for her, fresh whole food, using novel proteins that I bought at a (human) store near us that has everything imaginable, including python and alligator. She also got chinese herbs and supplements. But she kept getting worse it was just horrible. Finally she was having such horrific spasmic pain every day I literally was calling for an app't to put her down. She was 4 then. I kept begging our holistic vet for more help but she kept saying she wasn't in pain she was modeling off my own gut issues and that if I worked with anyone else she would no longer help us as it would "weaken what I do." She also at the point had gaslighted me into believing Sophie would be fine by the age of 6 if I stuck with her plan.
I have since learned a TON more about guts thru my own health issues and it now seems so freaking ridiculously stupid of me to have believed her and I'll NEVER forgive myself but I did keep trying with her.
At this point I told her I couldn't let her keep suffering like she was, she offered to take her home for 12 days which was nice of her but it turned out horrible. She told me she was doing just fine and would send me photos but her tail would be down which she never does unless sick or very stressed, and she said her tummy would gurgle and she would eat grass and regurgitated but that was "just her" and she was fine. I had told her the horrid spasms started early in the morning and would end in a few hours so was surprised she hadn't mentioned seeing that. But then one day she told me that every night she took Sophie out to their horse barn and left her in a crate all alone in the dark all night. She has horrid separation anxiety and claustrophobia and had never been left alone especially at night so the crate had to be pure torture for her! You can't crate a dog with those issues, some have had heart attacks, broken teeth and nails, even death. She told me that when she would go out to get her in the morning, she would have tipped the crate over upside down while still inside (it was a large size ruff tough kennel which weighed much more than she did) and she would have peed all over herself and spilled water on herself. Then she said "the only reason I am telling you this is because even through all that she is not having flares."
Well she wasn't watching her all night so she most likely did have those horrid excruciating episodes while they were in the house sleeping! Once they were done she looked fairly normal again so they wouldn't have known. I still can't bear to think of any of this. I will never get over it, I failed my girl.
When I brought her back home she was still having the terrible spasms so this "vet" told me it was because I worry about her (duh! She was suffering!) and that I needed to give her to a young healthy family with young healthy dogs and she would be fine. She kept telling me "you have to do what is right for the animal, not the human." I was beyond devastated. So we went to a local vet as a last ditch effort who put her on royal canin low fat canned (something I never would have considered feeding her) and her spasms stopped within 24 hours! It took her a year for her tummy to heal but now four years later (she's 8 now) she's 98% better no more spasms and has been for 3 years. We found out thru her internist that the spasms were from a functional ileus likely due to being so inflammed all the time. That is a hard thought for me to live with.
But I thank God many times a day every day she is now tons better!
She does have IBD though which has totally changed our lives. Excitement, fun and stress can set her tummy off. So we had to stop everything, training, dog shows, nosework, playdates with other dogs, visiting people, traveling, etc. All the things she and I loved to do. I had to quit my pet photography business (I owed her at least that!) and havent visited family, friends, no holidays, I NEVER leave her other than if I have to go to a Dr and be put out where I can't take her with me, (I have to go to the Dr a lot for my own gut issues) I get a sitter for her even then she often has a bit of a flare at least but it's the best I can do for her. Like you, I can no longer give hre ANY food what soever other than her canned RC, which makes training next to impossible since it's canned an mushy plus she loves to train so much she gets very happy and so driven to work I'm afraid of flares there too. She's never remotely as bad as she used to be but the fear of it going bad again runs our lives. I hate I can't give her the life I planned but she doesn't know what she is missing and I try to make every minute the best I can for her.
I do now consult with a holistic vet online who is much better than the "other one" we just tried super super slowly transitioning her from the RC (as much as I hate to feed her this) to Rayne low fat kangaroo. It took me weeks starting at just a minuscule piece slowly building up to less than a teaspoon but she started showing me signs I am not positive it was from the food but I'm afraid to keep trying. So she'll likely be on RC from now on. She also can't tolerate most supplements and meds. A few days on tylosin once sent her to the ER and hospitalized for 3 days having the worst spasms she ever did. I almost lost her. So we don't try things and I pray will never need to.
At this point she has mild reflux which I give her pepcid for, her stool is often too loose except first of morning is firmer but it does't bother her. The loose stool means she can't clean out her anal glands so we have to go to vet once a month to get them expressed which is stressful for us both as she SCREAMS bloody murder when they do it even when they aren't very full. We went yesterday and the screaming was bad. I do give her CBD which helps some. She also gets gas X if gassy, and she does tolerate digestive enzymes. Everything else we've tried with this holistic vet (that I love, Dr Katie Woodley in Colorado) she hasn't been able to tolerate. She does seem to have down days which I imagine is gut related but she eats well, NEVER eats grass anymore, and she bounces back. We also go for a half hour run at the park daily. And play at home. But keeping her life as calm and uneventful as possible is the key.
I also have to be sure she never gets one crumb off the floor or at the park or she pays for it. We have tried many different foods, ways to be able to get out more, etc etc etc all have failed so I don't try anymore. Raw is usually not well tolerated by IBD dogs so you know, (some do ok on it), anything with fiber really gets Sophie (now that I know more, it was the fiber in the pumpkin that vet had me feeding her and the high oxalates in the fresh ground herbs she had me giving a ton of as the main culprits that was making her so sick. Plus those herbs!) Also what has helped her a ton is 3-4 smaller meals a day much easier to digest than fewer larger ones. And nothing but a small bit of canned food with her pepcid before bed. I also warm her food before she eats.
So I do empathize with you for the things you and your boy may have to give up (and he may not have to give up as much as we have they are all different some IBD dogs can do much more than we can without too bad of a reaction) but wanted to share our story in case anything resonates with you. It's been very hard giving up our social life, etc but 1000% worth it to have my baby feeling so much better.