Cream doesn't dilute black, so if he were a smoky black, there would be black hairs somewhere in his coat that hadn't been affected, but I don't see any black hairs in the photos. Smoky blacks are normally all black, or only diluted around the flank, throat, etc.Adding to my last post too.... You said someone told you once that he was "purebred palomino" which is silly, but if they knew he had palomino in his parentage, i.e. they meant he was bred from one or two palomino's, he truly could be a smokey black as a palomino would have a creme gene to pass on, no?
Also, if he were out of two palominoes, I don't think he could have a black base, as Palomino is a red base, and two parents with a red base produce a red base (I think? Can't remember if e is dominant over black?).
I still think liver chestnut - I know a horse who is in between a liver and a chestnut and he has that real chrome sheen as well - Irridescence almost.
So I stick with my original guess - Liver chestnut with splash.