Gosh, im starting to think I should just message you directly to answer my questions! You seem to know everything. I'll definitely try out a bunch of different bits, the kimberwick works well, but I honestly feel like im cheating a little.
LOL hardly, I'm just learning same as you
But no seriously I had the same exactly problem and I recently switched him from plain snaffle to a french link and he loooooves it. He's so soft and happy and content.. not bracey and chompy and heavy.
But my original plan was try the french link, then if that sucks return it and try an oval link, if that doesn't work then a myler, and if that didn't work I'd probably go with a happy mouth.
I don't jump, just flat and my horse's mouth is extremely sensitive so we wouldn't do good with two sets of reins.
But really, each horse has their own preference for bits. Some are thick, some are thin. Some work different parts of the horse's mouth. Some horses don't even like bits.
It's best to try different things. Thicker pieces aren't as "harsh" as thinner pieces but too thick may not be good for the build of the horse's mouth. Some horses have high palates (high roof of mouth distance) and some have shallow. Some have parrot mouth, etc.
Do you see where I'm going with this? :P