Since "...there is no change…” at your check ups, this suggests that the lung sarcoid is not progressing. That, along with your pain-free joints and your "bumps" being gone, is a very good sign.
The swelling of your chest and weight gain around your "middle" are not signs of sarcoid but are common side effects of corticosteroid pills, such as prednisone, taken for the treatment of sarcoid. These steroid side effects gradually go away when the steroids are no longer taken.
You should have your doctor look at your armpit when you feel a lump, so that the cause can be determined. Also let your doctor know about the tightness after exercise so that he can determine what is causing this.