Relax. None of his uses compete with the originals. "Fair use" is a grey area. For example, see: https://www.etsy.com/seller-handbook/article/fan-art-and-fair-use-one-truth-and-five/39402098770
Besides, DC Comics, Marvel, Warner Bros, Disney, etc., are at the same conventions that Abe attends and are fully aware of all fan art. If he produced a movie, comic strip, comic book, etc., then there would be a problem. You can ask those studios yourself, as I have.