I used to shoot equestrian events professionally, covering everyone from pony club riders to multiple Olympic gold medalllists, so I hope some of what I'm going to say here will help. I especially enjoyed XC.
Comparing this with your previous version, it's a huge improvement in the processing. It won't be an option for you here as I see you shot this as a jpeg image, but if you'd shot in RAW you could have handled the shadow area around the horse's neck far better in the RAW conversion. That said, the shadow area is not too much of a distraction and you've caught a little bit of side lighting on the head which helps to lift the shot. I like your composition with the horse and rider filling most of the height of the image and being positioned left of centre, so there's a good dynamic feeling of them moving forward into the open space. Everything that should be straight and level IS, and it's well exposed. Nice white balance too.
I found it was always difficult to select fences where the horse and rider were well lit front on. I came to the conclusion that course designers must try to avoid having riders jumping towards the sun rather than pander to my photographic needs
However, I always walked the course and selected the fences to shoot based on a combination of how the lighting would be at the time of day when the fences would be in use, and how attractive or spectacular the fences looked. Fence designers also have a habit of decorating the side of the fence facing the approaching horse and rider, and not the other side, so a three-quarter rear shot such as yours is often the one which gives the best view of the fence itself.
The timing of your shot is just a fraction off. A tenth of a second later and you'd have had much better extension in the rear legs and, with luck, the fore legs would have been in a better tuck position. Certainly that's the shot we were always striving to capture, and it takes considerable practice to get the timing right so don't feel bad. I found I tended to slightly anticipate the shot, just as you have done, and so I would try to take 2 or 3 frames. (My camera took 10fps.) My 2nd frame was almost always spot on. Your camera can take 6fps so you might find that the next frame on motor drive would be a fraction too late. It's surprising how much moves in a tenth of a second. You could, of course, practice on other riders before your fiance reaches you to find what timing works best for you
On the technical side, I notice you've used shutter priority and set it to 1/1600th sec. Certainly you'd want 1/1000th minimum for this type of shot if that's possible, and 1/1600th should give good results. However, by using shutter priority, you have less direct control over aperture. Counter-intuitive as it might sound, I preferred to use aperture priority for my action shots. I had a couple of reasons for that. First, I like to have a short depth of field to blur the background more, which helps to focus attention on the main subject. That said, a blurred background is harder to achieve when shooting from farther away using a telephoto but with your f2.8 lens, you could have afforded to go with a wider aperture. Secondly, if the light changed a lot (as it often did) I'd not find that I completely missed shots because the fast shutter speed I'd set could simply not be achieved. If the light suddenly drops and the shutter speed remains fast, it might be that the aperture goes as wide as your lens allows but you still can't get a good exposure, so you can end up greatly under-exposing or the camera might even refuse to take the shot at all - not good. So, to summarise, aperture priority, wide aperture (that depends very much on your lens of course), and let the camera select the shutter speed. always keep one eye on the shutter speed and if it starts to drop too low, increase ISO. (Keep ISO as low as is practical though). A lot of experienced sports photographers prefer this method.
Your shot was 1/1600th at f8 with ISO 500. I would have set a wider aperture, probably f4 to avoid using the lens's most extreme setting, and a lower ISO. The camera would still have selected a fast enough shutter speed. Assuming it was okay to do so without getting in the way, moving closer to the fence and using a shorter focal length would have allowed a similar composition. With your focus point being relatively closer, you could have pushed the background a little more out of focus.
I noticed your exposure compensation was set at minus 1/3. That's a good idea because in processing images we can handle under-exposure much more easily than over-exposure. I would always aim to err on the side of under-exposure.
You've got a good shot there which is not far off being excellent. Although I've written a lot, that's not meant to suggest you've got a lot wrong. You haven't. I'm just giving advice and some alternative approaches which I hope will help you to get a real stunner next time.