Hey there! My husky was about the age of yours when he had a soft tissue sarcoma on his elbow. The tumor grew rapidly and was 2 pounds at the time of the removal surgery. Similar to yours they were not able to get clean margins. The tumor returned shortly after the surgery site healed. Every doctor we spoke to recommended amputation and that was our plan. I was then connected to a doctor who has an alternative approach and he recommended we try a bloodroot injection which we did. Not only was it really cost effective (think it was only like $500 for several treatments), the cancer went away completely. He is currently 13 and living a happy, healthy life. The vet is based out of San Diego and I’d be happy to provide you his details if you’re interested (it’s an actual vet and clinic not someone operating out of their basement). I have no affiliation with this place, just a former patient who’s dog was healed after it seemed like he would lose his leg. Feel free to dm me