I used to own a Paso Fino mare. She could be a fire breathing dragon if she was not happy.
I was boarding at a Paso Fino breeding farm. I bought her as a weanling. When it came time to train her I followed the training method in “Training Your Horse” by Vladimir Littauer, starting with a few months of lunging to get her strong enough to carry me and to learn her voice commands. I had no problems introducing her to work under saddle, slow, consistent, with plenty of “good girl!” and gradually creeping up the reins to establish contact.
This mare was EXTREMELY feed efficient. In the summer she got maybe 2-3 handsful of grain (oats) mostly so I could put salt on it. She was also on 12+ pounds of hay, usually fescue.
I broke her in a single jointed snaffle and had some difficulties with getting reliable contact. When I switched her to a regular Kimberwick she settled down. She had a small mouth, 4 1/2" and she did not like snaffles that were too wide, though later after my car wreck I needed a little bit more handle on her when she saw some juicy grass and we ended up in a 5" Walking horse curb with loose cheeks which let her move the mouthpiece up and down some. I had to give up contact with that bit but I had a good connection with her brain every step.
This mare was ardent. She was expressive and full of brio. I had to ride her with a lot more care than I had to use with my Arabians. If she did not like your riding you were in for an adventure as she expressed her displeasure clearly, sometimes at a full gallop (not me, I could ride her like she wanted me to.)
Paso Finos have a LOT of Barb blood, hot blood, ardent, brave, PROUD and eager to go forward. Not as patient with so-so riders as my Arabians, she thought she was super special and deserved good riding.
I get the feeling from your tale that breaking this horse to saddle like one would a hunt seat QH is a BIG mistake. Part of the reason I succeeded with following Littauer is that Forward Seat is ALL about the horse going forward with impulse so I was not going against her desires to go somewhere, anywhere, just go, go, go. I ended up riding her with a light hand and she was happy with that and I had no problems controlling her at all, she was loads of fun to ride.