Could a calcified granuloma in base of right lung found on x ray, be caused by gallstones/gallbladder problems? could it even be a gallstone?

Unlikely: If you have a competent radiologist, he/she should be able to tell the difference by looking at different views of the x-ray. If he or she was uncertain, he would have asked for further studies such as a CT scan.

No: 2 separate and unrelated findings. Calcified lung granulomas are common findings and “usually”, though not always, represent a benign lesion from either a prior, often asymptomatic, infection, inflammation or benign tumor (e.g. hamartoma). Usually, CT imaging is most helpful in assessment and ruling out other pulmonary abnormalities. Follow-up imaging often recommended to assure It’s benign nature

It Depends: A two view chest xray should exclude a gallstone as the calcification would project inside the lung on both views (front and side view). A one view chest xray is less definitive but generally gallstones are beneath the liver so shouldn't be that close to the lung.