Frankly, I think Jackson should just press forward with his claim and march straight to trial. He has the money to do it and that's really the only barrier to this sort of commercial litigation. Go get 'em.
When he gets to the courtroom door, the smart money is on New Line blinking.
There is nothing like the focus provided by a trial that is about to commence where there is a hundred million plus on the table - payable by one party to the other - that motivates parties to stop being asses and frickin' settle. If he allows his case to be dicked around in disclosure and discovery issues, this will go on and on and on.
Plaintiffs run to the courtroom; defendants run away. It has ever been thus. Get the bastards to trial.