Well, hopefully I help! I have a little bit of stage fright myself. When I'm acting, I just pretend that I'm leaving myself, leaving my body, soul, and mind, of stage, and that the character is acting for me.
I had to sing on stage before. It's defiantly nerve racking. But I practiced in front of my parents,my siblings,friends, and more. Try this. Also think positive about yourself. Thinking I can sing good, I'm a natural. This really helped me! I bet it will help you too :)
I can answer that....hypnosis. What you have is an unfounded fear that you've acquired over time. Anything you learn, you can unlearn. Hypnosis works at the subconscious level where the behavior is manifested and offers a suggestion that differs from the current behavior. If that suggestion is accepted, the behavior is altered and you now have a new "normal" behavior. Check into it. It works.