Haven't read all this thread, but I think I have the gist. I've worked with many different artists and I think one of the ways they learn to beat this is by taking control. Some do it quietly, empty dressing room for an hour before the gig, quiet contemplation, loosening the fingers and the voice. Others do it by ordering all the backstage stuff, the right sandwiches (that great scene in the dressing room in "Spinal Tap" when the meat didn't fit the roll says it all)the right booze etc. Others do it by being objectionable to all around them and getting them scurrying about and being obsequious.
I didn't need any of this but I still got the yips last year and had a run of gigs when I felt completely out of control and kept thinking I was going to run offstage any second. Surely they realised I was crap? What's the next line..the next chord..Oh God, help me!!
My wife told me when I confessed all this when it had gone that she never noticed, and if she didn't the audience certainly didn't. My last control mechanism, whatever it was, pulled me through.We all put someone else on when we go onstage. I think you have to find who that other you is.
. Tony Hancock used to throw up backstage before he went on live. Stagefright destroyed the career of Mike Yarwood, the finest impressionist comedian in Britain at the time. It can happen to anyone, anytime. I think the answer could be to examine your control mechanisms and work inside them.