I agree with Tiny, you are doing very well for your limited practice time. Your upper body doesn't bother me that much because how much you move from the waist up will always depend on the horse's movement. Some horses with smooth movement don't require you to move much to stick with their balance and other horses with big movement, you have to really use those abs and lower back to keep your seat down (which you are doing a really good job of).
I will also suggest you lengthening your reins a bit so that you are able to keep your elbows a little closer to your sides without getting them pulled so far forward, but the fact that they are going so far does speak well of your hands and their softness. Many people would keep their elbows back where they should be...and end up bumping the horse in the mouth with every stride because their arms aren't fluid. Your arms are fluid and I think if you lengthen the reins just a bit, your arms will fall perfectly where they should be.
I also notice that your toes point outward quite a bit and you also seem to have a bit of trouble keeping your heels down. That will come with practice and just remembering to work on it.
You are doing really well
Oh, and welcome!