No, pretty sure he was meant for fiend, considering that he sold his soul to a devil to become famous. Thats definitely a Fiend patron
I don't see any compelling reason to say that the only patron for Hexblades must be a Shadowfell entity. I could certainly see a Fiend-patron Hexblade. One of my character concepts for pen -and-paper is an Archfey-patron Hexblade.
For further examples, Fjord from Critical Role is a good example, he's a Warlock (Hexblade), Pact of the Blade, and his patron is "Great Old One" not "entity from the Shadowfell".
