His back is a little bit long, he stands camped out on the back and is cow-hocked. He toes out just a little bit on the front. None of these things are unusual. The only thing that bothers me even a little bit is that he appears to have a club foot on his right front. However, so long as he is sound, even that shouldn't be a problem. I like him, he looks to be a very sweet boy.
Love his face. What a great expression.
Like smrobs said, looks like a possible club foot. You can see the difference in hoof angle between the two front feet in the first, second and third picture. Talk to your farrier to see if your horse's feet are being trimmed that way because of confirmation and if not, have your farrier check the hoof angles in front. If your horse does have a slight club foot, a good farrier can alleviate some of the problems with a corrective trim.
I don't think his back is too long, at least not by picture #1 - but it's a judgment call and not obvious either way. I do think that his neck is a little thick and ties in a little lower then I would like. I like his eye and he has a sweet expression. He is definitely toed out on his LR foot and the club foot in the FL.
I had a great little mare a few years ago that could really work a cow. She was club footed but as long as she wast trimmed properly every 4 weeks, she never had a soundness issue.
BTW, I'm not crazy about the way your saddle is fitting or the position it is on his back - a little too far forward.
He's toed out on front and I agree one foot looks little funny, but I've seen club footed horses before and with the good farrier you can deal with it and keep it sound. Frankly, I don't think he has long back. Overall I really like him (he also doesn't look like arab, but more like qh IMO :) ).