I don't think that you should be spending any more time with horse alone, trying to fix things up. Why? Because you don't know how to fix it. Internet advice will always be conflicting & therefore confusing.
I suggest that you look up that "horse whisperer" & see if he can help, & if not, keep looking for the skilled horseman who will be able to, & show you how it's done.
It's time for the real deal: someone who's spent years learning to feel of & for the horse, & who can help you build a foundation of good feeling/respect between you & your horse.
Finding that person may take time, but "take the time it takes, so it will take less time".
Good Luck to you & your horse!