Tim, this is not an attack, and I'm writing this because of the possibility that it might help you to eventually be free of this. The opportunity is right in front of you, every minute of every day, to reframe this whole thing and escape the angst, but that will require you to adopt a new point of view.
I feel like the core problem is that you misunderstand this movie, and why it was made in the first place.
The first thing to be conscious of is that Steve attempting to beat Billy's 874K is not the point of the movie. The impression conveyed that Steve was the first to beat him is of course false, but it's also not particularly important. If it were, you might have a legitimate grievance, but it isn't. Steve attains his score at the 22 minute mark (which is actually a cleverly-edited conflation of multiple scores/submissions, but never mind, because that's not important either).
The bulk of the movie, and the reason it exists, is to depict the shitstorm that ensues AFTER Steve submits. The reason they made a movie depicting the shitstorm is because it lent itself to dramatically-compelling storytelling.
Contrast Steve's situation with yours. You beat Billy's score, it was accepted, he called and congratulated you, and you all moved on. But nobody would ever make a movie out of that, because it would be a movie with nothing to do. That is a straightforward, frictionless event, not a story. It's the antithesis of a story.
The value that Steve brought to the filmmakers was not in being "the first to beat Billy," because nobody outside of the classic gaming community cares about that. But a film-friendly story of a battle against unwarranted suspicion, nepotism/cronyism, double-standards, sabotage, and possible (now confirmed) cheating, all over a video game? That offered HUGE value. Billy, meanwhile, served as a spectacular villain, and the perfect foil for Steve.
So when you say that something which was "rightfully yours" was stolen from you, or that you deserve monetary compensation, or to have been in the cast, it shows that you're completely misapprehending what the commodity was here. The commodity was not a world record Donkey Kong score. The commodity was a story.
In the real world, the confrontation between Billy and Steve was actually about who would be the first to get 1 million points. Snip a few lines here, add a few there, modify a couple of graphics, and the movie would have played about the same, if not better, and you would have had no cause for complaint at all. The movie would have worked just as well with or without mention of your score, which had no influence whatsoever on anything that happened between Billy and Steve.
Yes, you deserved to at least be mentioned in the film, it was wrong for the filmmakers not to do so, and their answers to that question are disingenuous. If you were "owed" anything, it was your name in those on-screen graphics. But again, whether Steve was the first to beat Billy was NOT THE POINT, it's not why they made the movie, and the story did not rely on that being true. Acknowledgment of your score would have made little or no difference to the film that got made, and little or no difference to your life.
In fact, the irony is that you've probably gotten more attention and notoriety for NOT being in this movie than you ever would have for being in it. You also might want to take a look at how most of the gamers in the film were depicted and received by audiences. At least half of them regret taking part, for good reason. In all likelihood, you dodged a bullet.
You've been allowing Steve, Billy, Walter, etc. to live inside your head rent-free for a decade, based on flawed premises and totally unrealistic expectations and fantasies of what could have happened for you if you'd been included in the film. If you continue to obsess over this, they win. If, instead, you decide that there are very good reasons for you to let this go, then EVERYBODY wins.
