A.R.
Try these remedies that you can find almost anywhere:
Apple cider vinegar
Tea Tree Oil
Baking Soda
Apple cider vinegar bath ~ 1 cup apple cider vinegar in a warm bath for the hands and feet. Cider vinegar is a soothing anticeptic and neutralizes PH on the skin. It is also high in potassium so he will have some energy after the baths. Do this several times each day. Have him take a wash cloth and hold it on his face while in the bath to help with the sores on his lips.
Once out of the bath, use Tea Tree Oil ~ 4 drops in a cup of warm water, and wipe all sores with it. Tea Tree is anti-bacterial and cooling. It will also help to continue to dry out the sores.
Baking Soda for inside the mouth ~ 1 teaspoon in a cup of warm to cool water. Have him hold it in his mouth and spit back out again. He won't like the taste, but it will soothe the sores. Some will go down his throat and sooth the sores on his throat.
Do not put cream on his sores at all!
As with any skin sores, the more they can dry out the faster they will go away. When you put cream on a sore it traps the moisture and the bacteria inside making the sore grow. Regardless of the possibility of cortisone, don't use it. The carrier it uses is a cream-base which will have the opposite affect - it will trap the sore and make it grow.
Think about a cut and how it has to be clean and dry in order to heal. Sores are the same - clean them often and dry them out.
Once they start to dry out, taper off the baths. If it looks like you need to reintroduce or increase them, you can always draw another. Since babies don't sweat, two baths a day should do it to start.
Inside the mouth - stay away from oily foods: peanut butter and butter. Throat sores need cooling foods: frozen bananas would be great, cooled carrots, sweet potatoes. Give him a diet of cooled foods for a few days to give his throat a break.
If he is still taking a bottle, use real milk instead of formula. Formula has corn syrup in it which exacerbates any infections a child may have. Milk is cooling - even if it is heated slightly. You can warm milk slightly for more digestibility.
I don't envy you or your baby T. ~ my heart goes out to you both!