Keylight works best with a green background that's on the darkish side...and yours isn't. Keylight's putting noise into the subject. But you can salvage it by using the noisy keyed footage as an alpha matte for a duplicated and un-keyed layer. If your edges are good, you should be in pretty good shape.
It doesn't look like there's a light of green spill on the subject, but you can fix that once you have a good key.
it looks to me like the footage we shot log. You're going to need to do some color correction before you pull a key. Get the footage into the right color space and you should have a lot better luck. I can't tell anything about the noise because I'm looking at the footage on my phone.
Yep, what Rick said. That's definitely Log footage. I recommend using the Cineon Converter filter (under utilities) to convert it to linear before doing your key. Then, if you need to deliver in Log (if, for example the footage is being color corrected by someone else), then use the cineon converter filter again when you're all done to convert it back to Log.