Thank you to everyone who replied, both here and with PM's. This has been a roller coaster, and the outpouring of support really means a lot to me.
I have good news on the dog front: the original ultrasound, which showed the cancer spreading to his other organs, appears to have been mistaken, and it is still confined to his right leg. (The vet aspirated his spleen and the tests came back negative, and in his intestines she couldn't find anything 'suspicious enough to stick a needle in'). I'm going to call the vet to schedule his surgery later this week. He will have a long recovery ahead of him, but he can do it.
As requested, here is a picture of him. This was taken at Christmas last year.
