I have a feeling that this little horse's topline will lift with correct work. Rather than being a true swayback caused by lordosis... this is based on the second photo where it looks like a normal back as he's lifted his belly a bit.
That said, he does appear to have a longish loin - which will certainly be a disadvantage when it comes to building back strength as a strong loin is critical in maintaining a strong back.
His shoulder slope maybe on the steep side, though not critically, it's countered by a nice open shoulder angle. He has a fairly large shoulder as well, with a nice length of humorous - this should all work together to make him able enough to reach forward, and still have some scope.
I like his neck... it looks like the Saddlebred has really worked to his advantage here... as did the QH when it came to his hip.
While he has a nice hip length, and pelvic angle for riding purposes... this is hindered a little by how straight he is behind - unless it's an optical illusion from the angle of the photo. He will be able to track up decently, but, if that side shot is "true" of how he stands, he will lack the thrusting and sitting power of a horse with more angulation - this will hinder any real ability to excel in dressage (beyond basics). His longish loin won't help his ability to "sit" either.
Overall, he's a very cute horse... He has pretty good overall balance, and he looks like a very kind and willing horse.