Hello,
Sorry I can not help with the secific question as well, but glad you found this website. It has been a life saver for me when I had to come off of medications.
Concerning the diet... if he is responding that is good to hear. I believe in the leaky gut as a reason the bacteria are an issue for some of us here (gut becomes more permeable). If that is the case with your son similar to me, he is probably in a good position to take advantage of the diet. More NSAID's and alcohol you drink, the more of a leaky gut you may have IMHO.
So... if he is responding to diet, once he feels better he could try some what I call "fringe foods" that are a bit more safe that may allow his diet to seem more normal to other kids. These are some foods to look at...
1. Brown rice (more easily digested starch)... ditto quinoa, aromath etc... all of the whole grains.
2. Chocolate.... the darker the better. I have been eating quite a bit lately myself. I have been on diet for over 5 yrs now and needed quite a bit of time for healing gut due to past NSAID/alcohol consumption. But now I enjoy without issue.
3. All natural ice cream... only brand I could tolerate in states now and again was Breyer's, but you may want to check natural health food stores. I can eat ice cream down here in Argentina without issue... and it is sooooo good!
Of course for me, blueberries with yogurt (with probiotics like Stoneyfield Farms), pineapple, grapes, strawberries, cherries are always excellent treats... ditto raisons, walnuts, Craisons....
I would look into probiotics as well, maybe discuss with doctor first. But they are what really helped me turn corner with my personal healing plan.
Best to you and your son,
Tim