Not sure about this, but a guy at my husband's work told us how he was having a similar problem with his little girl. He and his wife (your husband may want to have someone come over and help)had the lock on the little girls door turned around for one night so that it would lock her in. I know it sounds bad but the couple stayed up all night to ensure her safety since she could not get out of the room. After an hour or so the little girl would get frustrated and go back to bed. Eventhough the little girl was up and down through out the night, the parents did not talk to her or go in and check on her. After one night the little girl did not get up the next night but the couple did close her door so that she would think that she could not get up and go get in mom and dad's bed.
However I don't remember how old the little girl was, and would be concerned about the impression that you instill in your child about their trust and dependablity in you.
Maybe you could do a compromise between the what they did and what your husband has been doing. Use the child gate, when your little boy gets up tell him to go back to bed so that he knows your there and that you hear him, he is not alone, but do not go get him even if he cries and screams all night. I know it is hard, but thing I have learned is that if you can be tough for one day and not give in you can usually rid yourself and your child of alot problems you may have.
Good luck, and be careful while deployed. Thanks for all you do. D.