Regarding the Doom curing Ben deal...From everything I've heard so far I think it may well play out like this:
Reed is working on a cure for them all but falls just short (as he always did in the books) But Doom, whom no-one knows was also affected yet, takes Reeds ideas and
is successful in making them work (in the books Doom did cure Ben at one time where Reed had failed).
He offers the cure to Ben (who doesnt know Victor has gone loopy yet) who leaps at the offer and it's only after the process and Bens humanity is restored that Doom reveals his own transformation and true intent (that's pretty much spelled out in that wizard spoiler). It's also clear from that spolier that this Doom is
revelling in his new power, he isnt gonna give it up without a fight.
From there Doom will take down the rest of the FF, forcing Ben to to reverse the cure and become the Thing again for the final battle.
Now for that final battle this is more what I hope they have gone for, rather than it being anything I'm in any way sure of:
For whatever reasons simply taking Doom down isn't enough to stop his danger, perhaps his power is growing too much to a level where it could destroy the city or something (there was a mention a while back from the FX guys working on Doom that his power is "his undoing").
The only option for the FF is to use Doom's own cure on him which they try, but Doom himself tries to bugger up the process, causes a big explosion (destroying the device so Reed can't figure out what Doom did to it to make it work and it cant be used again) and once the smoke has cleared Doom appears to have dissapeared.
We find out in the closing scenes that he did survive, was indeed restored to human, but his face got torn apart in the process (and at least by the end we have a Doom thats closer to the comics). Now powerless, horribly disfigured and a wanted felon, Doom flees the country (as per that mention from our source of Doom being smuggled out of the country in a crate. Apparently on a ship bound for Latveria).
Well thats my best guess, atm