You have a big heart!

I agree that the first thing is to get rid of the fleas. Capstar will kill what's on him. Revolution once a month will keep them off, protect from heartworms and some other worms.

Cataracts CAN be removed successfully, if you can afford it. You would have to see a veterinary opthamologist. Otherwise, I'd let him 'map' your house and yard on his own. Maybe lead him to the water dish, door, etc. until he gets it down for himself. Walk heavy (not quite stamping your feet) so he can feel the vibrations. Put scents on doorways or a rug under the water dish. He will use his nose to find these things.

For the arthritis, add some glucosomine to his diet and be sure he isn't overweight.

He can live several more years. My dog is blind, has a thyroid problem, and is diabetic. He has been for over 4 years and at 13 is still getting up on the furniture and smelling out the dog park.

Mary