What Causes Swelling, Breathing Difficulty, Cough, Sweat, Blurred Vision For A Diabetic?

My husband has swollen up like a balloon. 15-20 pounds in water weight. He saw his Dr. yesterday and he put him on 40 mg of Lasix Bid and Metolazone 2.5 mg, Bid. and has scheduled an echogram for April 15. He is having trouble with losing his breath, coughing, and of course the swelling. He, also has diabetes which runs between 115 and 125 before meals and then 2 hrs. later dips to 58. He begins to sweat, gets weak and has blurred vision. He doesn't seem to be able to get enough food in his body and eats continuously for a couple of hrs. and then the symptoms go away. This happens 3-4 times a week. His Dr. stated that he has never had any problem with his heart pumping before and doesn't think that it is congestive heart failure but ordered the echogram, in case. He told him to eat food high in potassium while he was on the water pills and to check back in 2 weeks. If this isn't congestive heart failure what else could it be and where can I get a list of foods high in potassium and is 4700 mg a day enough considering he's taken the water pills.