Weren't the Dorrance brothers cowboys??
OP, yes, sounds like a rotten deal all round. I would recommend you find a good trainer, hopefully one that will teach you
along with your horse. If you don't want to/can't find a *good* trainer, to fix the mess it sounds like that woman(wouldn't call her a trainer after your story) made of your horse, the only other option is to do it yourself. So start educating yourself
Sounds like you've made a good start.
While I'm not a Parelli follower & have some probs with some of his newer stuff, I think his book & basic principles/lessons - eg. '7 Games' are a great help in teaching people how to teach/deal with/listen to horses. Clinton Anderson & some others seem very similar to Parelli, so it comes down to which style/personality you like the best I reckon. Also re understanding your horse's bodylanguage & behaviour better, I think Parelli's 'horseanality' stuff is worth reading - just don't let it encourage you to pigeonhole your horse though!
Another thing that I reckon is invaluable to learn, no matter what style of training/riding you want to do is learn the principles of behavioural/learning psychology/training. Sounds heavy but not really
& I think learning the principles behind 'clicker training' is probably a good place to learn the gist.
**You can spend any amount of money on Parelli stuff if you so desire, but you'll find all the basics online for free.