Strictly on the bucking issue: my OTTB used to buck after mounting if I didn't lunge him prior. My instructor told me to pull inside rein "up and in" towards your belly button. I would do it when I would feel him "think" about bucking (along with a Hey... in my warning voice). Mid buck I would also pull up and in and he would stop. That's what worked for me, its sort of hard to explain but riding with elbows in at your side, move your hand/wrist straight towards your belly button (best way I can describe it).