A little reminder in these Neil Gaiman times:
Abusers groom allies as much as they groom victims. When they get accused, they need to have a list of people who will say they could never. They go out of their way to help you. They're funny and charming. They want you on the witness stand in their future trial.
If you got groomed as an ally and not as a victim, you would have no way of knowing who they are behind closed doors and you're not a bad person because you believed them.
The only thing you can do now is decide what to do with the information you have. That's the only part that is your responsibility alone, and you can choose to Sunk Cost Fallacy this shit or you can choose to be better. That is the one choice the abuser has left in your hands, make it wisely.
Sunk Cost Fallacy also applies to how invested you are in an artist's work. How much it defined you. How much it helped you through the hard times. How you imprinted onto these characters and let them share the burden of living with you for a while or a lifetime.
As a veteran of the 2007 Harry Potter internet forums, I am here to tell you that you did that. Neil didn't do that. The lessons you learned, the ways of being you adopted, the comfort you found, you did that. Neil Gaiman wasn't in your library nook or bedroom or study hall or apartment walking you through it. You consumed An Art and applied it to your own life because you are a sympathetic human being who wants to find community with other human beings.
The lessons you learned are yours. They aren't tainted by his behavior because he wasn't in your room telling you how to feel. You were feeling on your own. Take those lessons forward into something new and better.
None of this is an excuse to keep consuming his intellectual property and I will judge you hardcore for doing so, signed, the girl with a HP tattoo who hasn't read HP or fanfic in over a decade.
You don't get to keep it because it was important to you. It was important to you because of who you are, not because of who he is, and you can bestow your precious sympathy and attention somewhere else going forward. I believe in you.
Godspeed, little angels and demons.