Hmm, ok, I'll give you bits of advise here, but my one main thing I'm recommending to you is to look into Cesar Millan's books (Amazon.com has good prices on them
). I've read them all and his phylosophy on dog behavior is invaluable to me.
Just really quick too, as far as his nuetering, if you can't find a free service, it's much easier to find a "discount" spay/neuter service. If you lived close to me I'd know exactly where to tell you to contact, but maybe try contacting your local ASPCA and ask them if they can direct you. Nuetering won't solve all your problems, but it will help some and you definatly want to do it for the other reasons - pet population (you never know, if he ever God forbid got loose or something) and it helps prevent testicular cancer etc.
Ok, first - even though he's being good for you on the 20 ft. leash, I'd still spent a majority of your walk making him heal. It will teach him that you are the "leader" not him.
As far as your problem with the door, it sounds really severe and I know you can't afford a trainer (since you're not able to neuter him) but that would be my first and formost advice since he seems to have gotten to that "red zone" with this situation.
Practicing alot is what I would do. Take him for a very long walk, till he's
tired then get him to be relaxed in the house. Have a friend or even another member of your household go outside and knock, BUT don't give him that chance to come running to you biting. Stand in between him and the door and FIRMLY say "NO" when he barks. Hold your ground no matter what, don't let him to that door. Block him from biting your legs if you have to with a pillow or whatever. Hold your "alpha" position there until he backs down. You'll have to repeat this as much as necessary till he gets the point.
I don't want to keep going with too much because I really think you'd get alot more out of reading Cesar's books than I can type here and this case is serious since he's inflicting harm to people.
It's probably likely that, like you said, at some point someone scared him when you weren't home since you said this just started, or it could be that he's trying to show dominance, but sounds more like anxiety causing the agression and he's redirecting that fear-agression towards you instead of the door or who's behind it.
My #1 rule when I get a dog is right off the bat, they KNOW that
I (and my husband and son) am alpha in
any situation (I follow all of Cesar's rules and do alot of socializing to differnt people, places, noises and situations). Sounds like (from what you've posted) you really need to establish this on a basic level before you'll have any real success with the door knocking problem. Even if a dog gets really afraid of something, if they look to you as their "leader" and you are calm and uneffected, they will follow that responce.
Good luck, keep me posted
