I am slightly confused, I can't seem to help the shopkeeper with his whole quest. I'm not real good at riddles, and I tend to be repetitive. Can you give me hints on this whole "Heat Occisia"?
first, after seeing the shopkeeper condition, go home, study the shopkeeper disease, you should talk with lizardmen priesstes, ask her how to make heat occisia. then you can check the ingredients in the "cauldron" menu (i don't know what is called) and you can make the heat occisia right away
just 1 potion is enough for him to be cured. To make Bernard drink the potion, you can approach him in his place in daylight like usual. The dialog box will explain the condition of Bernard. Etc
normally, the next day after you give medicine to him, he will be healthy again. maybe there's some bugs or anything else that make this happens. i suggest you to DM the creator to seek for solution.