Wow you look excellent! It's not the best picture but from what I can tell you look very good. Turn your toes in a tad. Your horse looks very good too. He looks like he'd be a nice eq horse, not too big of a bascule. Lovely knees. You both look very nice.
I would like to see your hands lower. There needs to be a straight line from your elbow through your hand to the bit and your hands are too high, almost as if you were trying to lift him over the fence. Practice releasing down either side of his neck. Other than that you look really good. I like that you are looking where you are going!
You already mentioned stiff shoulders, so that's covered. I wanted to point out how stiff shoulders will cause they entire arm to ... rebel (for lack of a better word).
Your forearms are tense and raised, they need to be lowered with your elbow relaxed and easily ready to give. Your forearms can almost rest on the horse's neck to provide smooth but independent hands from the bit. (No jerking or clinging to that bit!) I disagree with having a straight line from your forearm all the way to the bit. It's not practical or correct in my eyes.
I think you also need not to turn you toes in but rather roll your thigh inward. Having the inside of your thigh resting on the saddle will correct your toes. Turn from your hip, not your ankles.
But you do look very beautiful. Your horse is lovely and picks up very well. I think you have very few flaws in this picture - well done.
I actually like your hands. They are in a line to the horses bit. I would say your ankle is a little harsh. I would like to see a softer less flexed ankle joint. It looks a little forced and as a result the toe is turning out.
I'll critique the dressage photo;
Your horse is very lovely, but looks to be in a forced frame. This could be the reason your hands are low and wide. I'd like to see you soften your elbow and bring your hands in while turning your wrist, you seem to have piano hands. If your horse is not in perfect frame, do not worry. Having a proper body position and a free and forward horse will win over a perfect head set. Once you move up levels, your horses frame will develop.
I can't really see your leg and seat position here, but I believe that you need to let your stirrup out a notch. Your thigh seems to be positioned correctly, adjusting your stirrup is more then likely the reason behind your forced and crooked ankle. Merely bringing your heal back up without adjusting your stirrup may cause your knee/thigh to move forward giving a chair seat affect. In dressage it is not essential to have such a flexed ankle. A good seat will look the same standing up as it does in the saddle. The ball of your foot should be placed on the stirrup with an elongated leg, generally resulting to a horizontal foot rather then a heal so far downward.
I would like to see you stand in your stirrups after lengthening them and then sitting in the saddle evenly on both seat bones. I believe you were taught jumping before dressage, correct? Your seat comes off to me as a jumper transitioning to dressage. Arching your back will resulting to hollowing it. A straightened back on even seat bones (with elongated legs) is correct. A braced back will be used in later test (if you aren't already using it at times.)
I really like your shoulders - they are back but relaxed, very important. Remember not to eliminate relaxation by trying to over correct your seat. A perfect seat that is tense is still incorrect. Relaxation is key. Your thighs are placed very well, something many riders struggle with and your hips do not seem collapsed, another important thing. Yours bridle looks to fit, your saddle seems to fit due to your leg position although I can't be positive because of the picture. Your head is up but if I were judging I would like to see you looking forward with a soft expression, let few know you're working hard! I would also recommend white gloves, they are much more classic and would give your soft hands a lovely look.