The first thing that comes to mind is to marvel that you were able to ride around in a busy street for these pictures.
With the CAVEAT that I'm not an expert fitter, here are my thoughts:
- Just eyeballing the saddle fore-aft, it looks like your knees are behind KOPS, which isn't a good or bad thing, but that you probably won't need to scoot the saddle back any further.
- It's hard to tell with the rain jacket, but it looks like you are rounding your lower back and keeping your arms fairly straight. Whenever I have lower back pain from riding, it's because I allowed my back to round rather than rolling my hips forward to allow a flatter back. The flatter back then allows you to look ahead without craning your neck as much.
- I've had wrist and shoulder pain in the past from locking my elbows with straight arms -- keeping my arms loose with a deliberate bend has helped a lot, but it took vigilance to break that habit.
- Finally, you may find that your fit is on the aggressive side for really long riding. I like zipping around on a bike with lots of saddle to bar drop, but my rando-specific bike is set up to be more upright, with the drops position about where most roadies would have the hoods position. Hope this helps.