First off, what a cute horse! He looks like a very talented jumper. I agree with everyone that says you've got a good leg. It's nice and tight, pressed against your horses sides just beautifully. Do you do a lot of dressage work? No stirrup work? What ever it is you're doing with that leg, it looks like it's working. As for your upper body, you'll fix all that with a good approach to your fence. In the photos, your shoulders are stiff, you're catching your horse in the mouth with your release, and you're not balanced over the fences. But that's all okay! You look like a very good rider and it looks like you've got a good horse there who will take you right to your fence, so you have the perfect opportunity here to learn how to jump properly. Here's an exercise you can use:
Set up a crossrail. Trot back and forth over it repeatedly. As you approach your fence, get into a quarter seat and press your hands forward, into your horses crest, making sure your hands aren't interferring with his mouth. Your hands should be farther up his crest then in either of the photos you've supplied. (A quarter seat is accomplished by tilting your upper body just a few inches forward. Your butt should be only just out of your seat, this is basically a modified half seat/two point). This position will allow you your horses body to come up to you, creating a two point over the top of the fence. If you need to grab mane to stay nice and stabilized, do so. It will only make your release more effective. Let your horse move freely forward for a few strides when he lands, whether that be at a trot or canter, staying in your quarter seat, before sitting down and asking him to come back to you. When you feel very confident with your ability through this exercise, move up to a canter, doing exactly what you've done in the trot. You'll develop a working relationship over the fences with your horse, a sense of your center of balance over fences, an understanding of your distances to fences, and an effective position and soft hand.
Overall, great job! If you decide to get into jumping, I'll think you'll be quite talented at it; you really look like a very good rider. As for that dressage saddle, I agree with you that it's a far better choice then a stock saddle, but the problem with using a dressage saddle to jump is it puts your body in the wrong place for jumping. Over small stuff it won't make a horrifying difference, but if you ever decide to move up with your jumping, you'll need a different saddle. If there's one you can borrow that will fit your horse, that's what I'd do.
Good luck with your jumping work and if you decide to check out my advice, post on how it goes!