Thirsty? Drink and and Number 1 a lot? Have you been checked for Diabetes?
Always good to ask a doctor but here is some off the cuff advice. Maybe the 2 conditions are not related. The heartbeat is frequently felt or heard in an ear just because of the closeness between the eardrum and a blood vessel.
Dry mouth could be as simple as failure to drink enough fluid in a hot environment, Of course there may be other dry tissue in your body. Sjogrens Disease (sp?) This disease includes a dry mouth, poor gum condition, possible poor dentition.. Hope you ger relief soon. Perhaps your Family Doc or/ and an endocrynologist can answer your question regarding the annoying dry mouth. Hope this info helps a bit.
Do you also feel thirsty and need to drink water very often? Also do you get cramps? If so have your vitamin D level checked.
might be to do with the 7th facial nerve that controls salivation and also runs near the inner ear.
when did it start? did you have any other symptoms in the weeks before it started?