I won't mention the jumping photographs as this is not my area of knowledge. Dressage/flatwork however, is.
As tinyliny said, your position on the grey bareback is good. But your position in the saddle does need some adjustments.
The first thing I notice, is your tendency to grip with your knees/thighs. This forces the lower leg back, lifting the heel and preventing you from applying sensitive leg and seat aids. The gripped upper leg also tips the upper body forward, and thus you are bracing your arms and having a hard time staying with the horse's movement.
A gripping upper leg is detrimental to the horse's training, as you are blocking the movement of the shoulder, which prevents the forelegs from being able to move and extend as freely as they should. As a result, correct lateral work will be difficult to achieve.
In some photo's your arms look fine with good bend and a nice soft contact. In others though they are straight and stiff, leaving you unable to feel the contact and making it near impossible for the horse to come onto the bit or even into a contact. This will make the horse hollow and stiff.
Some homework for you.
Fix the gripping upper thigh before worrying about anything else. It's going to hurt your hip flexors to start with, as they won't be used to being stretched and open, but it's an essential part of your riding. If you watch a truly talented dressage rider, their knees and thighs will be loose, even floppy on the saddle. The upper legs do not play a part in balancing the rider.
I want you to practice turning your knees off the saddle, keep them nice and loose and relaxed, allow the thigh to relax and hang. When you turn, open your inside knee even further off the saddle, and close your outside thigh onto the saddle. if you practice this enough, you will be able to turn a horse purely by opening one knee and closing the other ;)
When you have the upper leg/knee sorted out, I think you will find that your lower leg 'hangs' at a better angle and your leg aids will become much more effective. Your horse will begin to open its shoulders, I think you will be pleasantly surprised at the improvement of the horse's paces and willingness to work.
Fixing the knee should also sort out the upper body tipping forward, but you may need a small amount more help with that as it has become habit. Try to imagine that you are flashing your chest to some gorgeous bloke on the side of the arena ;) Or, what I like to use with some students that are quite ambitious, is to imagine that you are riding down the centre line of a Grand Prix dressage test in front of a huge crowd. That'll make you sit up, be full of self confidence, and ride like you KNOW you are **** good, if you know that you're good, you'll ride like it :)
As for the hands, I know I have said this many times, but so far it's by far the best exercise I know for 'fixing' just about every problem with a rider's hands/arms.
Get yourself a crop or dressage whip. Lie it over your hands, with your thumbs on top, with a space of around 10cm between your hands. Firstly, this will force you to keep your hands with your thumbs on top, and an even contact on the reins. Secondly, because your hands are in line, your elbows will be in line and your shoulders will be in line - it's all connected ;)
When you ride with the whip like this, I want you to keep the whip around 5cm above your horse's wither, with the whip never coming behind the wither. Keep the whip level, so that if it had a spirit level in the middle, the bubble would always remain in the centre.
Try riding with the whip on different sized circles, maybe place a witches hat or other kind of marker in the middle of your circle, and concentrate on keeping the point of the whip directed at the marker. This is where your hands should be positioned when riding a circle.
Hopefully this helps you a bit!