Overall, your design of position is good; you're sitting directly on your seat bones, with an flat, relaxed, upright back, and the correct line through your ear, shoulder, hip and heel.
To my eye, you're riding at the correct stirrup length for english hunt seat, and a little short for western. If you're going to be sitting the jog and lope, you may find this shorter stirrup pushs you up out of tack and makes it harder to maintain a deep seat. If you spend a lot of time out of the tack or standing in your stirrups, regardless of the type of saddle, then your stirrups are a good length. Pay attention to the amount of bend in your knee; and then look at other good western riders - you'll see that their knee angle is more open.
Can't tell about saddle size from these photos; but here's a general guideline. If you feel locked into the saddle, and there's no room to comfortably slide your seatbones forward and back with the horse's motion without bumping into the saddle swells, then yes, the saddle is too small.
I'm not going to critique your hand position as I'm not really sure what is correct in western equitation. In the second photo, your hands are high and artificiall looking, but I'm sure that's not where they are when the horse is moving.
For English equitation, you're slightly large for this horse. The height of your upper body is disproportionate, adn your leg is slightly too long for the horse's barrel. For Western eq, I think you're fine. For pleasure and trail riding, absolutely fine.
Nothing glaringly wrong.