I'm just seeing this now. What a very difficult time for you and Dye. I hope that you don't have to resort to amputation, but if you need some encouraging words about how well they adapt here are some. Like many others who have posted here, we had to amputate Snickers' front leg due to osteosarcoma. I don't think the vet followed the protocol recommended by OSU (although I gave them the literature!), so she had more bruising than necessary but the overall outcome was a dog who was her "old" self -- jumping, playbowing, running, happy. It is hard emotionally for us to think of it, but dogs bounce back and cope well. Dye's quality of life will be fine. It's a rough couple of weeks post-surgery but once you're through that it's business as usual.
Please update and I'll be thinking positive thoughts for Dye.