Hi K.,
I really do feel for you. While I know this is a difficult time for both you and your son, there's no excuse for your son to disrespect you and other people(and pets). Obviously, you are trying different methods. Is your son's routine the same as it was before your husband left? It is really important that everything in your son's schedule remain the same (other than the fact that Daddy is not there). And if Daddy was the one who usually did the discipline, you will HAVE to step up and take over. The time out works if you do it consistently, and do not argue or reason with the child. Give him a warning..."that is bad behavior, if you do ___ again, you will go to the naughty spot." Then set him there, tell him why. Do not look at him or talk to him (or show that it's upsetting you!) And then when time is up, tell him again why he was there and ask him to say "sorry" then give him a hug and say "I love you." This is all straight from SuperNanny, but it does work. I have a difficult three year old daughter, and I'm thankful that I follow this.
My husband was in the military, and I've been through the deployments myself. Try to make friends because they'll be a great support system for you. Best wishes and hope things improve for you soon!
R.