I don't know if I am going to repeat any other comments but I havn't read previous posts
In most of the pictures you seem to have a bit of a chair seat - this being that the lower leg is too far forwards. There should be a straight line from the ear, to the hip to the heel. A good way to check is if you look down you shouldn't be able to see your toes. I would perhaps put the stirrups down one hole, but that is up to you. To get the lower leg back and down you really need to open through the hip. Do some exercises like no stirrups, leg stretches etc to open the hip and allow the leg to fall back and down into the correct place. Once the leg is further back you can then work on securing the lower leg around your horse and allowing the weight to flow down into the heel naturally.
You look like you are leaning back in some of the pictures. Although you want to be sitting tall, you don't want to be behind the movement.
To me, the arms and hands are not in a good position at all (no offence). You need to carry them higher. There needs to be a slight bend in the elbow, your hands should be carried and the thumbs should be facing upwards.
Your horse is not working properly, he is on the forehand so not using himself correctly.