Tummy issues take time. It sounds like you have done a lot in a very short period.
I would suggest overcooked white rice, soupy and mushy, until you get a log poop. This may take a couple of days. Then add a small amount of cooked white chicken with no fat to the same rice. Gradually, over 3 days or so, increase the amount of chicken until you reach half chicken, half rice. If at any time you get loose stools, take a step back and let his gut settle.
After you get solid poop on the chicken and rice mixture, start substituting a small amount of the chicken with the BB kibble. Go through the same steps as before, gradually upping the amount of kibble and decreasing the amount of chicken and rice until you are on all kibble.
If at any time the gut gets inflamed again, you have to step back and allow things to settle. If the BB proves to be too rich, you may have to search for a lower protein and fat content food to feed.
Gut problems are rarely remedied in a couple of days time. Every time you switch his diet up, you run the risk of aggravating the gut again and starting all over. Patience is the key.
I would also recommend a vet visit to rule out any issues that may be contributing to the problem.
Good luck! And I hope your pup is feeling better soon.