What all the other people here have said...Let it go. You can walk away! You CAN, and you don't even owe him that much of an explanation. You are a caring person, and you think you've invested this much time with him, and want to make an impossible situation work out. All his behaviors are worse than anyone should put up with. You seriously need to just let it go, walk away, and get on with your life.

Speaking from experience, when you end a relationship like this, you may very well have a period of withdrawal, where you want to contact him, or wait for his calls. Be strong, and eventually, you will be so GLAD you did!