There are times when the fact that someone is asking a question means they already have an answer. They just don’t like it. I think you already know you should probably call off the wedding. That doesn’t necessarily mean that you should end the relationship. But you shouldn’t take the next step until you and your finance have had a chance to work through the very serious issues that you presented in your letter.
Your fiance is a wounded warrior who is fighting many internal battles. He may not be ready to be a full partner to anyone, even to someone he loves as much as he loves you. I hope he is in treatment for both the PTSD and his recovery from alcoholism. I hope you have been invited to be a participant in his therapy either through some couples work or through occasional participation in his sessions. He has work to do to learn to trust himself and trust another. He is probably working on gaining confidence that he can manage his inner pain with his own strengths instead of with alcohol. As for you: Many women in your position need to learn some ways to help the partner cope and to keep themselves from being pulled into his issues.
My guess is that he wasn’t trying to deceive you. He was presenting the person he wishes he was instead of the wounded person he is. Now that everything is out in the open, he needs to show you that he is wlling to do the hard work to turn his hopes into reality. This is going to take time. Only you can decide whether you see so much potential in the relationship that you are willing to be patient with the process.
I’m truly sorry that you have been so terribly disappointed. But I do think it’s better for you to figure these things out before you get married.
I wish you well.