My herding dog/terrier mix still marks a lot. (in and out of the house) He was neutered at about 18 mos, I know it was done right because I was a tech at the vet clinic that did it. Watched it done. He still marks, still mounts, and still chatters, clicks and foams if he gets near a bitch a heat. He's a bit over 9 now. I think how much effect neutering will have on behavior is very dependent on the individual dog.
This same dog had severe anal gland problems. They would get impacted and infected. After several infections, we finally had them removed, but he still occasionally scoots, the vet can't find anything. I think he just got used to it.
My mom's current dog needs her anal glands emptied about once a month, but has never had them get impacted and infected like Petey's got.
EDIT: I think you did well with the ACV and pumpkin. Once he is on good food and his stool is more solid, he wil probably be able to empty the anal glands himself.
This pic on wikipedia, WARNING, GRAPHIC: http://en.wikipedia.org/wiki/File:Anal_gland_abscess.JPG shows a pretty severe anal gland abscess, but that is similar to what Petey's would look like, placement WRT the anus is about the same, but his glands were much smaller, and usually would get infected on both sides. My mom would say that they looked like giant blueberries. Made it hard for me to eat blueberries for many years.