9/10
I really like him! It's an interesting design. I agree that the back mark looks out of place. Leaving it white might look nice, though you could probably get away with continuing something similar to the legs pattern. I do like the little detail of the braids near the fron legs but they seem just a smudge out of place since the hair doesn't see me very long there? Otherwise I really like this character! The small details like white on the hoove area just make it that much better.
I'm not very good with names but traditional russian names would be neat? Or just traditional names associated with royalty.
------
I know most people don't like humans, but I thought I might throw him out there to get a low rating. He lives in a realistic world so he's not anything special. This certainly isn't his most interesting outfit but it's the one on the ref, so hey. Mostly I want to focus on him being distinguishable.

everything my me
-He's rude. Like, he doesn't know when to shut his mouth. One of his closer friends has had to drag him out of fights he stated without meaning to multiple times.
-Narcissistic. He actually does have the personality disorder. It's something he works on regularly and has gotten better with as he has grown closer to his friends.
-Once he trust someone, he really does. Usually he avoids putting trust in people, but once he does he can kind of come off as dependent to people outside the relationship.
-Despite all the things that might make him seem otherwise, he's fairly reliable. Since he's honest to a fault he's unlikely to give someone bad information unless he's trying to. If he promises something, he makes good on it since he's surprisingly good at self discipline.