Baron, my 125lbs body builder shepherd. That's what a friend of mine called him. Went the same way. At the end I had to carry him everywhere or he'd drag his back legs bloody. I knew it was coming but I was avoiding it. 911 happened and I had to deploy, which meant I had to put him down, no one else could carry him and I'd be away a longtime. When we took him the whole family held him as he slipped away. Even the vet had tears in her eyes. There are still tears in my eyes.
I'm so sorry for what you'll be going through.