The 322-pound, redmeat-loving Dorchester dad who stuffed his face with pizza, steak tips, prime rib and fast food in a final fling before stomach-shrinking surgery, found out yesterday that the gravy train has reached the end of the line. His surgeon won’t operate until he drops 40 pounds and gains some new perspective. “It couldn’t have went any worse,” said Chris “Tiger” Stockbridge, 34, who claims he’s a changed man, finally ready to follow doctor’s orders and submit to a life of oatmeal, salad and fish, if that’s what it takes. “I felt a little bit ashamed of myself,” he...