1) I've played several different Keeper variants against Gro over the last 6 months. I played Paragon Keeper against it last FNM.
2) In my experience it's a tough matchup. No surprise there. Basically, if I resolve Abyss or a Strip Mine hits home, I win. If I Mana Drain their first 2CC creature, I can often gain control. If I have to play catchup, trying to find point removal or tutor for solutions, I lose. I went 1-3 at FNM, though I believe my opponent opened with Island->Emerald->critter in most games. Its very difficult to come back once you get behind the curve and have to react to their play. Generally, I do better than that (or Gro does worse

, I'd say 50/50 is a pretty realistic assessment, though it depends on the exact version a lot. I generally crush the UWG version (6-0 in tournament play, against good players), but a good player with a UG version is more like 50/50.
3) I bring in ReBs and 3xKegs. "Keg for 2" just slaughters the versions with few creatures. Bring in as many Kegs as you can, even at the expense of ReBs. I SB out Mis-D'able stuff like Mind Twist, 'Geyser and Stroke. I like to keep the Tutors in since Gro is so vulnerable to Abyss or Strip Mine. If you play Trinity, its not impossible to keep the Stroke and try to win after gaining control. One horrible flaw in Gro is that they have to show you their hand to Land Grant. Ugh. (I'm not sure why Gro players havent moved to the Fetch Lands; being able to do free tricks with Brainstorm and Land Grant doesnt seem worth showing your hand at the start of the matchup. And fetching basic Island is so important to this crappy mana-base.)