Next visit. Make sure you tell him on your next visit. He/she should have asked.
Its ok but. People forget all the time but please bring it up asap. Smoking is a major risk factor for many diseases that will make your life miserable and lead to your untimely demise. It's difficult to quit, so ask your doc for help.
No... Your doctor needs to know you are a smoker because smoking increases your risks of certain disease like COPD and some cancers, including lung cancer. Smoking cessation can help prevent these diseases and your doctor can help with quitting. So, you need to tell your doctor you are a smoker as well as how much you smoke. It is important for your health!
He knows. Unless u smoke one cig a day there is no way the doc did not smell it as u deep breathed into his face while he got up close and personal with ur tonsils.