There is nothing wrong with the Ability. Marvel Scale is NOT Milotic's HA. It correlates to Swift Swim on Feebas, meaning that were any of those 3 Feebas to evolve, they would be Milotics with Marvel Scale.
As for the moves... TM moves have always been odd to me. In my own experience, sometimes they pass down and sometimes they do not. I haven't found the pattern myself, and my go-to info site, Serebii, doesn't go into specifics on their breeding page with respect to TMs. I've tried looking on Bulbapedia, but I always get lost trying to find *anything* there.