A.,
I have worked in the medical field for most of my life and I have to tell you, you are doing great. It is very common to get diarrhea with teething. The bananas are great for binding and keeping his potassium up. I agree with no sugary drinks because it can add to diarrhea. The water for hydrating is fine and so is his normal drinks, just increase frequency because he is loosing fluids. If the exudate or snot is clear, he probably does not have a virus or bacterial infection. If the snot is green, most likely bacterial infection, if it is yellow, most likely viral, if brown, blood is mixed in the snot, and keep an eye on the color and moisturize the nose with vaseline or normal saline rinses. I hope this helps. There are many other symptoms to accompany rotavirus, since you didn't give any of the other symptoms, it doesn't sound like rotavirus, so don't panic. Tylenol is the most common and safest drug out there for infants/toddlers, unless he has an allergy. I wouldn't worry about giving him any other medications, because once the tooth comes through, most of the snot and diarrhea should dissipate. I hope this helps. Just give him extra TLC, and the BRATT diet is helpful, B=bananas, R=rice, A=apples/applesauce, T=tea (not necessary for kids, mostly helps with sore throat), and T=toast, but most breads and grains are good too to firm up your stool.
Ali