I just put my Boxer to rest a couple of weeks ago. Many of the signs you describe sound very familiar. She had a brain tumor. I decided to let her go as long as she still had some dignity of walking on her own. She lived for protecting me, cuddling and wagging her behind. She could not do any of it anymore and she did not know what's going on most of the time. She looked so peaceful........I know it was the best I could do for her. It's never easy - No matter when the point comes.......but you have to think about her now. What would she want? What does she need? Hang in there.......