Don't know when your subscription expires, but I'd recommend waiting a week or so to upgrade as 4.0 will be available soon. It shouldn't be a stomach churning update, but will have some improvements that will be required by Facebook later this year.. so might as well wait and only do one upgrade
As for comments, that's unfortunately not possible. We'd love it if there was a setting we could manipulate to disable commenting for some users (ie not logged in, don't want more comments on a page, etc), but Facebook doesn't provide it. Their feeling is that if the user is logged into Facebook, they can comment using the Facebook comment box.
Sorry that's not the answer you're looking for, but hopefully, it's not a deal breaker. As a moderator, you can of course remove any comments you don't want and you should get a notification whenever they happen. Not the ideal fix, but it's something.
Finally, please check out our signature on how you support JFBConnect by leaving a review.
Should you need anything else, you know where to find us,
Alex