Well grandpa seems to sense when Warlow is around so i find hard to believe if Ben were Warlow he would not know, or have a sense of it somehow. Here is a thought, could Warlow be half fairy and half vampire? He comes from Liliths time so who knows. As for Ben, if he is not Warlow maybe he is working for Warlow.
I don't know how attuned his senses are, because the last time he thought he sensed Warlow it turned out to be Nora.
Yeah, I had the same thought about Warlow possibly being half-fae, or having consumed so much of their blood that he's taken on some of their properties, much like Russel being able to walk in the sun after feeding on them.
Ben working for him makes sense to, though I have to wonder why they made such an effort to conceal Warlow's face if he wasn't going to appear under an alias first.