Your hand/arms look good, I've always been told that you should have a straight line from your elbows, down the reins to the horses mouth and its like perfect. Your stirrups look about right I judge it by putting my legs straight down and the stirrup should land at your ankle. But I like mine short so I feel its personal preference. You look good just maybe a little stiff but good position ;) Better than mine I've always had problems with my hand/arms
There is no such thing as a "correction bit". No bit can "correct" training or riding.
You should be riding in a simple bit which allows you to ride correctly. Never should a leverage bit alone have that much contact on it.
Saddleseat is the only English discipline where a curb bit with contact is acceptable. You wouldn't be allowed to show her like that, if you had any plans to do so.
Just ask next time why you're not working her in a simple snaffle-- she'll get HARD on that bit if she's bein' ridden with contact like that all the time-- we currently have my show horse in a snaffle to restore softness, which is restoring headshake.
Your horse is a great mover. You need to put more weight in your heals and get them down. That will help you anchor in the saddle and stay put. Her head should be placed at wither or just above with a definite arch. Make sure she is on the bit and not behind it ( you get dinged heavily for that). Also work on getting her to hold a consistent headset. Otherwise you guys are looking good.
Ps. Work in a snaffle and if you need the leverage go to a kimberwicke but remember soft hands.