You registered back in December!
You are probably one of the oldest folks around
(Try our premium section in the Forum for some more exercises - you now have access).
As to 610 on Kaplan. I would say it is 680 on the GMAT - don't sue me if you get less or more, but that's my general feeling. Sounds like a very good inprovement.
As to RC, there are a few books on AMazon, but all of them have horrendous ratings and 1 star - your best shot is just going over RC passages and reviwing Kaplan's Verbal Workbook now and then.
IN addition you have OG - so you can practice there a lot, but you should take PP before you do that. I guess you know that yourself.
Probably the most important part in OG is CR since GMAT's CR is different from Kaplan's and PR's
Thanks for the probability tip - how much is it by the way?
BB