What is lymphedema?

I need to learn more about lymphedema.
When Eugene's left lower leg swells, his blood pressure goes down. This is daily. When he gets up in the morning, his leg is not swollen and his blood pressure is high. By early afternoon his blood pressure is low and his left lower leg is swollen. He will lie down for an hour or two. Then his leg will not be swollen and his blood pressure will be normal.
In 2022 he saw a doctor for large clear blisters on his left leg below the knee and was diagnosed with PAD. Last month a doctor said his right lesser femoral artery was 100% obstructed and he could not open it. He told Eugene to talk to his cardiac doctor because blood pressure is not a vascular surgeon's specialty.
January 2025 he was taking four prescriptions for high blood pressure. He got up after going to bed, checked his blood pressure and it was 64/40. I gave him a salty snack with water and had him reclining with his feet elevated. I couldn't get systolic pressure above 78 so I called for the ambulance. Hours later the ER doctor discharged him with paperwork claiming he had LOW blood pressure and he was dehydrated. I had verified pitting edema at his left ankle. If I had been with him in the ER, I'm sure I would have needed bail money.
About fifteen years ago he had a stroke which affected his left side. December 2023 he had open heart surgery where they took veins from the inside of his left thigh. He has had a swelling the size of your open hand there since then. The swelling increased in size after the angiogram this month, but that doctor denied it was possible. He wouldn't even look!!
He is a diabetic. His A1c is 6.0 and he has lost nearly a hundred pounds. Now his limbs are thin and his belly is fat.
He will see his primary doctor April 1 and his cardiologist around the end of that month. Since he will have Medicare then, I hope somebody will do something. Any advice will be appreciated.