In both of the non-jumping photos, you appear to have your pelvis tipped forward and your back hollowed. This will both affect your balance and increase the overall tension in your muscles which will also affect your horse's movements and tension. Remember: the better you balance and the more relaxed you are when riding, the better your horse can move in relaxed balance.
Understand that a horse's responses are often -- I might say usually -- the result of how the horse is ridden. In your groundwork, concentrate on riding in a balanced and relaxed manner. Try to help your horse understand than she can relax even when being ridden. The more relaxed you are when riding, the better you can follow the movements of your horse. As your horse becomes accustomed to your two bodies moving as one, your horse will begin to respond to slight changes in your movements.
Begin this work while riding on the flat. As this becomes second nature, start going over ground poles and very small jumps. Concentrate on your balance and following your horse's movements. Trot over a very small jump; then, try to get your horse to walk a couple of steps after the jump by simply sitting up and stilling the motion of your seat. As your horse stops trotting, let your body begin moving in the walking motion with your hands following the movement of your horse's head and your seat bones following the motion of your horse's back. When you can do this regularly, you may start going over higher jumps doing the same. Realize that your horse may need a couple extra steps to go into a walk after executing higher jumps.
This relaxed movement may take some time to develop. The time will be shortened if you suspend your jump work for a while. As you develop your relaxed riding, your progress should develop more quickly. If you do not learn to ride in balance, relaxed, and following your horse's movements, you will likely continue to struggle.
In his book "My Horses, My Teachers", Alois Podhajsky wrote of his experience as an international jumping competitor while in the cavalry. His stated that his jumping improved dramatically after he reluctantly began dressage training at the "suggestion" of a commanding officer. He would win jumping competitions against much faster horses that had better conformation. Podhajsky later became the director of the Spanish Riding School in Vienna, a position he held for more than twenty years.