Pretty sure this hasn't been mentioned yet -
If I were you, I'd do what you've already done, but also see if you can get in touch with a rescue group in your area that holds adoption events. I am sure that they'd be happy to list your dog on their websites and let you attend adoption events with it, so long as you make it clear that you'll keep it and pay the bills.
The only problem that I can see with this is that many rescues have a spay/neuter contract, so they may require you to neuter him, but may not want to take on the cost. But it can't hurt to try. And maybe, just maybe, you'll find a group that will be willing to neuter him and take him under their wing, with you as a foster.
ALSO:
As for petfinder, in the rescue work I've done, I've found that it can be a great tool, so long as you use it to your benefit. First and foremost, you can't get a real listing unless you are posting through a rescue group. So if nothing else, try to find a group that'll let you post as a crosspost. If you don't do that, all you'll be able to do is post a classified, which may work but wont get nearly as many hits (and you can't include a picture).
Next:
Take a good picture of the dog. Preferably landscape (as they show up bigger in the thumbnail that you see on the listings page) Make it catchy. I've seen people take pictures of the dogs and then crop out the dog so there's a white background behind it. That'll catch interest. I've seen dogs dressed in hats and sunglasses - it makes you want to click. Also - professional quality photos with just a simple backdrop (even a picture with grass in the background) makes the dog stand out more. But you NEED a picture. You wouldn't believe how much it 'ups' the # of visits to the pages.
Write a bio that people want to read. The point of the bio is to get someone interested in the dog. Be honest, but flatter the dog's good points. If he kills cats, a simple "I'm a sweet dog that knows I'm a dog. I'm an expert cat chaser, so if you're a cat lover, you may want to look elsewhere" will work much better than "may kill cats. Chases them."
Good points to flatter:
housetrained
obedience trained
non counter surfer
low shedder (though if he sheds buckets, it isn't his fault!)
not destructive
non-chewer
non digger
non fence jumper (mention height of fence)
calm and relaxed in house
good with kids
good with dogs
good with cats, horses, brids, etc.
Friendly
low barker
small/medium/large size (and why it's so great!)
make sure you also make it clear; however, that some things can change in different environments... so don't swear that he'll never pee in anyones house. Instead say: "so far, this dog has been great! We haven't had an accident yet, so we suspect that he's housetrained"
Hope that helps... just realized that I wrote a whole essay, so I'll stop now.
-GoingNowhere
