GMAT Plan

I'd think of like this: if you're at 500 now, and you know you want a 650, then I'd aim to be consistently scoring above 670 on practice tests so you know for sure you can rock a 650 on Test Day under pressure. That means you're looking at a 170 point gain, which is a lot.

Is this do-able in 60 days? Potentially, but you need to work smart, not just hard. Your first step should be to really assess your weaknesses. The materials you mentioned are great, but there's lots of students here who have completed hundreds of GMAT questions and read those same books without the resulting score they wanted.

Try to order each Verbal question-type from WEAKEST to STRONGEST then go through the list, attacking concept by concept. If you only have a vague or fuzzy idea of what questions are your weaknesses and strengths, then I'd go back through your last 100 or so incorrect practice questions (either from books or practice tests) and log them in an Error Log. That may you'll have some data to analyze for commonalities.

Though I'm not sure of your exact score breakdown, I think a 90-day study plan might give you more time to confidently get into the upper 600's. Good luck!