That doesnt even look like the same horse as the first pictures. Im leaning towards grey arab X now with a bloodspot.
You really need clean whole body pictures of him without any tack. Full body in good light, clear photos....and a clear, well lit head shot so we can see his face. Im thinking one good set of photos will clear up alot.
I think he's pure arab. More of a traditional arab than the new showy arabs, though. He looks a lot like my friend's eqyptian/polish arab cross. He doesn't have the extreme dished face like you see today, but the extent of what you see now is generally bred into them-much like the height has been to warmblood breeds. I know Hanoverians were originally bred for the German cavalry and as cart horses.
I've seen many arabs that just have all of their flee bitten spots concentrated into one area-which is what his splotchy areas look like. Sometimes instead or in addition to having flee bitten spots all over their body, they will accumulate in different spots, from what I've seen they tend to be on shoulders most often.
I agree with Greenas. Seeing him move, he screams Arab to me, I don't really see much of an indication of other breeds. Even if he is mixed, he's mostly Arab for sure...maybe a quarter or an eighth something else.
My half Arab fatty Caleb has the same kind of spots on the right side neck ear and face (non/very few on the left):