Went to the vet last night and the dog decided he wanted to stick around a while longer. Perked up and actually walked around the vet's waiting room looking totally cute and later ate something by himself (not force-feeding), so doing well, or as well as can be hoped at this point.
He got another IV for nutrition, and IV antibiotics and painkillers. Currently he is on painkillers and high-calorie food to try to keep his weight up-- really skin and bones after not eating for so long.
We (vet & I) don't see him lasting particularly long, but if he is determined to stick around a while, I am thrilled to have him, so all is well right now.