I think getting him neutered is an excellent Idea.
I have not read this entire thread so this may have been mentioned before, Trying catching a few episodes of The Dog Whisperer. He is a dog psycologist and can help you to figure out why he is aggressive and show you how to work on those issues and to develop trust in you, even if he has fear aggression.
If you do not get the National Geographic Channel, you can go to his website,
Welcome to Cesar Millan's Official Web Site.
Good luck, I think with some love and understanding and patience he will come around.