I think that Ink, TOWTM, Pinstripes and Bill Roberts are all the same person. Even though different people describe him differently they always reference him in relation to some other prior event. In the prior event, he is often described in a different way.

Example: In Chapter 23 part 3, Kalani says the man in the hallway is the one from the arena, and Riley describes him as having a disfigured hand. The one that attacked the tower and killed Paul was described as having tattoos, a pinstripe suit and his hand was shot by Burt.