How to force a journal to address an associate editor's scientific misconduct?
I don't know the details, but from what you've written, I think your case is somewhat weaker than you think it is:


You can't be sure the first reviewer is your competitor. You can conjecture, but you can't prove it.
Even if we assume the second review is bogus, it doesn't mean the editor made a decision based on it. It's possible the editor is making the decision based on the strength of the first review, and simply included the second review because it's available.
You say that the associate editor published two papers at the same time you submitted your manuscript. I don't know what typical review times in your field are, but this implies the associate editor submitted his papers long before you submitted yours. In other words, he has precedence.
You imply that the associate editor wrote papers and gave talks that say X ("Snow is white") but rejected your manuscript because of ~X ("Snow is not white"). This sounds ridiculous and my feeling is that you're missing something subtle. For example, maybe the associate editor is saying "green snow is not white" which isn't contradictory with "snow is white".
It sounds like you are charging both the associate editor and the original handling editor with academic misconduct. This is clearly a more serious accusation than normal, because it implies both of them colluded. You're further accusing both editors of collusion with the reviewers. My gut feeling says at this point you're stretching belief. I'm not saying it's impossible, but it absolutely sounds unlikely and the burden of proof is heavily upon you.
Further to the above, you don't actually have strong proof. You only have suspicions (which is actually a good thing: it means the reviewer anonymity shield is working). What you've written is somewhat contradictory as well. You say that this journal is one of the oldest and most respectable in your field, and yet the associate editor has published two papers in even more prestigious journals.


If you're convinced your position is correct, I'd escalate the dispute, first to the EiC (which you've already done), and then to whatever is above (e.g. the publisher, the society that manages the journal, etc). Keep in mind however that these people cannot break reviewer anonymity, because that mechanism is in place precisely to prevent authors taking revenge on reviewers for rejecting their manuscript. In fact part of the reason the dispute is where it is is because the associate editor (naively? bravely? you decide) signed his name on the decision.

If nothing happens, my conclusion is: the more formerly-uninvolved people come to the same conclusion, the less likely it is they're all colluding against you, and I'd just submit elsewhere.