@camlich Wow, camlich. I'm a bit tongue tied about what to say. First, I don't have the medical experience you're seeking, but I can understand why your heart is seeking answers. 8 years isn't nearly a long enough life for a dog. The last month must have been a roller coaster. I'm so sorry.
Like you, I came to this site shortly after my pup had passed. For me, I found it extremely healing to be able to talk about it, post pictures and memorialize his life with us. Know that while we may not hold the answers you seek, we are here to support you nonetheless.