Dude, sorry your dog is sick and all, but it's time to let it die. It had a good life, but the thing is suffering terribly. Had a dog for almost 12 years get cancer and she collapsed too towards the end and couldn't walk. I put her down myself. Yes it's hard, but you're deluding yourself in thinking a 14 year old dog is going to live that much longer.
Sorry for your loss. Pull the plug. Mourn, then move on with your life.