Hey this is really great work.
Beautiful to look at and an amazing achievement. The modeling texture and fur work on the dog is fantastic. The face and eyes. It all blends together so naturally and convincingly. I’m sure many here clearly know how hard that is.
I would agree a bit that some secondary movement in the standing posture would help in the future. Some very subtle drift and twitch. Also possibly some sign of breathing in the rib cage area. I would expect him to be breathing quite fast and be slightly more twitchy after moving around so quickly. Small dogs twitch and fidget all the time. Although really this is a tiny little criticism. The works stands.
Did you use any dynamic effects for the fur ? I just ask because I tried something similar to this some time back with a small feathered dinosaur. I needed to go back to an earlier version of Blender as the dynamics were badly broken in later versions. It seems it won’t get fixed until 2.8 as the plan is to totally re write it.
Anyway all the best.