I haven't read through all the post, however, the one thing I will not "do" is random rearing. IMO, it is the single most dangerous "habit" a horse can have. A trusted horse that might, for justifiable
reason, go up and you can give them their head and go forward is "expected"...one that just does it out of the blue...no thanks, you never know if they have sense enough not to do it in a precarious situation or have overestimated their own "athletic" ability w a rider on their back. If it were me, I would find a well respected trainer that had a lot
of success with overcoming the problem in the past.