I'm not an English rider, so take this FWIW:
I thought there was a lot to like about how you're progressing. Some of the things I liked (I took these snapshots and will leave them on my imageshack account for a week or two, then delete them):
1 - Your lower leg seemed pretty stable. I started at 50, and my hips were so tight that I gripped with my knee for the first 2-3 YEARS. It is also tied to
2 - Your posting looked natural. For the first couple of years, my daughter would post with an exaggerated forward thrust of her hips, making her look like a Jack-in-the-Box. She's much better now, but you looked relaxed and your body and legs were unfolding and settling. You looked balanced both at the up position and the down.
In the picture below, you can see I often tilt too far forward. Maybe because of the saddle, or maybe because I have the least natural talent of any rider I've ever met
. My horse doesn't seem to mind, but I'd bet the old injury to my lower back would ache a lot less if I'd get more upright:
In my defense, I do better on the trail...I stop thinking about my position and relax:
3 - Your hands seemed stable. There was a little slack in the reins, which is how I like to ride - enough slack that I'm not all over my horse's mouth, but tight enough that my pinky can take some of the slack out and let the horse know what I'm thinking.
4 - You are looking up and out. Good!
Now, not so good.
I like a chair seat for some things, but I'm weird. The saddle is causing part of it, but your feet are too far forward. What makes sense to me is to assume that for any given saddle, my rump should be in the lowest part of the saddle and the stirrup straps should hang down straight. Those are the things that make gravity my friend. Any time I deviate from that, I'm fighting gravity. And gravity usually kicks my butt.
If you imagine where the stirrup bars are, and draw a line straight down, that is your goal for your stirrup position. Using that criteria, I'd say the saddle is causing some of the forward foot, but you are causing some as well. But remember, I'd have been thrilled just to not have my legs flopping around like chicken wings at the same point...
When you slow, you put your feet forward. I do that too, but most people say it is wrong. I also do it regularly when riding. It stretches my leg, relaxes my leg, helps me get my heel down and my horse relaxes - probably in response to my leg relaxing. But it also has some drawbacks, and it is better not to get into the habit.
It also looks like you are looking at your horse instead of up and out.
Overall, I'd say you are making great progress. Lots of what you once knew is coming back. Nice looking horse, too.
When I don't overthink things and just relax on my horse, riding does lots of wonderful things for my body.
Oh - and remember to slather on the sunscreen. I love being out in the Arizona sun, but at 54, I can promise it is hell on the skin! During my years on the flightline, I had a long sleeve flightsuit on - but my hands are starting to look like an 80 year old cowboy's.
And I'm going in to a dermatologist in a couple of weeks to have moles removed from my face & a biopsy on them...Mr Sun has kicked my butt!