I got the ME report today. It lists the Cause of Death as "Lobar Pneumonia". The report said "Bilateral lower lobe pneumonia", which is bizarre because he wasn't even coughing on Monday, yet he died Tuesday morning. Not that I'm disputing the findings - based on what the autopsy report said, I can accept that as the cause. It doesn't say what caused the pneumonia, but based on how fast it happened and the reading I've done online, I'm guessing it was bacterial. I'm going to my doctor's office on Friday with a copy of the report, hopefully he can help answer the few questions I have left.
There's a little bit of comfort in the thought that it was a sudden bacterial infection that overwhelmed his system, because it means that it wasn't "something he did wrong" or "something I did wrong". I had thought that the painkillers he had been taking had contributed, but the autopsy report didn't say anything about it (even though they did blood tests). It also means that the two working theories we had (gastric hemorrhage or pulmonary embolism) were both incorrect, and I'm glad that they did the exam.
There's also a little bit of comfort in the thought that with as fast as his system crashed, I don't think there was anything that we could have done differently that would have changed it. And also he only had a short period of time that he was uncomfortable... and an even shorter period of time to be afraid between knowing "there's something really wrong" and losing consciousness.
It still hurts like hell and I miss him like crazy, but it's another question that's been answered and that helps a little bit.