Just in case the problem isn't quite solved, here is another possible suggestion. By the way, what kind of bug did he eat?
I have been monitoring your previous threads on Shadows problems, and it sure has been an ordeal for all concerned.
Something I have used in the past on my animals having mouth and digestive problems is Aloe Vera juice. It could be worth a try. It does have a healing and soothing ability when taken internally, as well as aiding in digestion. I would try to get 2 teaspoons of Aloe Vera juice into Shadow over the day using an eye dropper. I would administer two eye droppers full at a time, and taking a few minutes every time. Administering about a quarter of an eyedropper each time you put it in his mouth, and try to apply it in both sides of his mouth to make sure the whole mouth gets coated with juice. An eyedropper will take about 1 ML so you will be giving Shadow about five treatments a day.
The juice I use is Lily of the desert, and its marked "Preservative-free". It does have a pH stabilizer in it - citric acid. There are a couple of other good quality brands out on the market but the names are not coming to me right now.
Check out the organic apple cider vinegar and see if there is a way that you can use it as well. There are a lot of benefits to apple cider vinegar both to us and our pets, I have an apple cider vinegar and soda every day (scotch free). The people that got me started on apple cider vinegar used to put it in their cats drinking water, and it was a small amount so as not to affect the taste of the water too much, and turn the cats off of drinking.