The good news is that the spot they saw in his lungs is gone now and his kidneys seem fine. The bad news is that he has dilated cardiomyopathy, which is a disease where the heart is enlarged and the walls of it have subsequently thinned.
Hobkin's long-term life expectancy isn't good. The disease is fatal. However, he may still have some quality time left with us. The vet couldn't give us a precise estimate; he said anywhere from days to months.
He's already on the meds he needs to be on—pimobendan, furosemide, and enalapril—and will be on for the rest of his life. My preliminary research has come up with a couple additional treatments (i.e., taurine and L-carnitine supplements) which I'll want to bring up with the vet as well.
Finally having a proper diagnosis eases some of the helpless frustration I've felt this last week, but knowing that Hobkin is indeed dying makes me anguished and tearful. I am grateful that it seems likely we'll have some time left with him, just not as much as I wish we had.