GREAT improvement on standing tall! It's OK that you're leaning back, if it's from the ankles and the body is a straight line, which you are.
Next thing to work on -- use the legs more -- more knee bend, more reaching back with the hips. Pattern with a kettlebell deadlift then try to bring it to your swings. More ROM will put more load on your big working muscles, not your back. Feel the glutes, hamstrings, and quads all get loaded in the backswing and get put to work in the extension/upswing. To keep the load off your back, keep the abs tight and use the power breath.
Also on your set-up, get in position before hiking kettlebell back. Reach back with the hips, load the hamstrings, pack the shoulders, chest up and forward (flatten the back), get tight.
Great work and let us know how it goes as you keep working at it.