If you want my opinion dude, unless you were actually planning to try and make money from the character, don’t do anything. Marvel can afford much better lawyers than you and as haven’t copyrighted the character, they will chew you up, spit you out and probably counter-sue and get you to take down the character. I don’t believe that digital date/ time stamps count as evidence of when something was created, as anything digital can be edited/ tampered with, so it isn’t concretely provable. But I only studied music law so I don’t know about if the same standards are applied to literary creations.
We won’t do anything in terms of removing the character, so you don’t have to worry about that.