A couple of thoughts on FARA and Bell's change in tail rotor design:
First, I don't think it's fair to say that Bell changed the design after RCS requirement were lowered because it was realized that low RCS was incompatible with the pusher ABC configuration. That would imply that the requirements were lowered to allow the Raider to compete sometime after Bell showed its initial configuration. At that point, Sikorsky had already shown its design; they'd always said it would be based on Raider. Frankly, it had to be, because Sikorsky has invested so much in X2 technology with not that much to show for it, that they had to go with an X2 design or else abandon it altogether, and frankly, it's all they've got for the future. They can only push S-70 technology so far. On the civil side the S--76 is gone and the S-92 is based on S-70 technology. On the military side, they've basically got further refinements of the H-60 and the CH-53K. Not anything that has got long "legs" except X2 if they can get it to work better than it has so far.
Regarding pusher propeller and RCS, it's worthy of note that except for Bell's 360, all of the candidates used pusher technology, so clearly that wasn't considered an RCS problem by anyone, including the Army, from the get-go. RCS reduction wasn't a constraint even when the RFP went out. Low RCS reduction requirements like Comanche was trying to achieve was not required because top Army along the way finally acknowledged what their operating forces were trying to tell them years ago: Except for highly specialized limited uses (like searching for Bin Laden,and even then the airframe program was terminated early), trying to make a "stealthy" helicopter is a dumb idea. There are all kinds of reasons for this, but here's just one: Why go through all the pain and suffering to reduce RCS on something that the bad guy can just look out the window and see?
Besides, who cares about the pusher when you've got that relatively large mast/hub on an X2?
I suspect there were other reasons why Bell abandoned the fan, maybe something as simple as it looked more like what the Army is used to (although they'd never admit that), and in a competition every bit helps.
As for the admittedly strong resemblance between the planform of Comanche and Invictus, similar requirements can result in similar shapes. Look at the F-14/15 and the MiG-29/SU-27. Bell would not have access to Sikorsky's proprietary data from LHX,and what flight data would be public probably wouldn't be enough to be that much of a driver.