This looks great! You pick up really quickly! :)
Here my thoughts:
- I wonder if you should rotate the head towards us a bit on x0 (for that pose) as he looks back, so it's not so 90 degree rotated
- around x48, when he's sitting down and has his hands on his legs, I would bring up his shoulders, so we can feel that he's propping his arms on his legs and therefore pushing the shoulders up a bit
- as you spline this, you can add a little overlap in the head after x50; his root comes to a stop and that sudden stop makes the head go down a bit (imagine walking and stopping quickly while keeping your head loose, it would bounce forward and down, finishing the forward momentum)
- moving on to spline, you can start thinking about finger poses so they get out of the generic x0 & x62 poses
- you might have to extend the shot a little bit, but maybe not; right now he leans back and you almost want to feel how the back hits the chair and stops and the head does a little overlap there
That's it though, looking great!