Looks pretty good. I assumed it was a commission at first glance.
Maybe you'll feel brave and try the whole body one day

One day for sure. but before that, I have to eradicate my weaknesses in anatomy and proportionality

No better way to improve your anatomy than to study anatomy. I mean really study it. If you're going to draw animals (humans, dragons, horses ect) then knowing how they're put together is everything. You don't have to look at gross stuff to do it. With animals like horses, ultra-shorthaired dogs, hairless cats.....you can learn a lot, assuming you get good poses. Follow that up with anatomical illustrations and cross-reference. Maybe find a 'volunteer' for testing how the body looks in various positions, and test range of motion. Regular treats recommended! It can be a lot of fun And knowing anatomy will make drawing animals far more fluid and fun.

As for proportions - especially with unusual perspective, I got nothin'. However, I do know a few artists cheat by creating a basic, rough 3D model and posing that to get their proportions for 2D.
Would you say you have a fairly critical eye?

I don't now, rather not, I think. All I can say is that I can only draw what I see. Most of the time I'm looking for references that are the most suitable for what I have in mind.

It was just a vibe.....
The point I would make is not to be afraid of 'failure'. Don't do like I did, and quit if it gets hard to meet your own expectations.
You're off to a good start. Keep at it.