Point #3 is probably what sold many of us on the FFR. To play devils advocate for just a minute, do take time to look at the frames of some of the more recent players (in the last few years): JBL, Cutting Edge Replica's and most notably, Hurricane Motorsports. Kirkham actually has an accurate frame too. All four tend to have frames as good (or better if you ask others) as Factory Five's. You should visit those forums too so you have a well rounded opinion.
I personally wanted a race frame and at the time, but with a predetermined budget. Ladder "only" designs just doesn't seem good enough to me, for serious racing. If I were just doing shows, cruises and promo work with the car, then I would of looked for the kit with the most accurate body and details; frame isn't all that important; they all tend to serve the purpose and in fact, some have raced with some success. But nobody talks about whether or not they actually do any stress analysis. (Someone on FFCobra.com took the time to do something of that nature and found the FFR frame to be pretty rigid.)
As for point #1: that's purely a function of the whole brake system you decide on. Remember, with kits, you can put in ANYTHING you want; you don't have to compromise unlike production cars, but be careful what you ask for!
Having said that, I believe most of the 4 mentioned use good brake system; FFR is the only one (if you're going donor) with a farily sedate brake system but as many will say, it's a brake system for a 3200 lb. car, going into a 2400lb. car. But everyone that decides to do serious racing upgrades the brakes anyway.
Point #2: I think they're all pretty much the same; about a 48/52 IIRC assuming all equipped equally and all being 90" wheel base.
Point #4: If you're referring to track in terms of turning left and right in addition to straightline, you may want to look a bit closer at the aftermarket that supports FFR. Gordon Levy has some setups that can hook you up any way you want. But if you bought any of the 5 kits mentioned here, I'd say JBL by it's reputation is the best handling; but it's a stretch when it comes to "looking" like a Cobra replica. From the outset, it was designed for racing.
The CER is another that was engineered chassis-wise by a Sprint Car racer and uses the unconventional inboard shock/spring setup front and rear. Very cool setup and I'm assuming it would work well on the track.