The "small bulge" sounds like a hiatal hernia. Have him see a gastroenterologist.
I just read your thread under candie1982's post that was duplicated here.
"What are his doctors missing?"
I don't know since you failed to mention the types of doctor's seen by your father. Has your father pointed out the "small bulge" to the doctor and/or doctors? Was it just a primary care physician who saw you father? Was he referred to a specialist? It would be nice to know what they had to say about this too. Therefore, without knowing what they did or said, I would concur with peek's statement about seeing a gastro to diagnose your father's abdominal issues. Have him/her check the pancreas and the liver for issues too. Be prepared, this may require extensive testing requiring an assortment of visits to the doctor's office and/or hospital to get to the bottom of his ailments. Good luck.
No, I don't think a 74 y/o man should feel that way, every day of his life. He sounds miserable.
Can he get another opinion? If he's only seeing a family practitioner, he may want to see an internal medicine specialist. Or possibly a Gastroenterologist, since the problem seems to primarily in his stomach, and with nausea and stomach rumblings.
I'm not at all sure this has anything to do with diabetes. Only a doctor would be able to sort that out.