Hi flapjack29,
First congratulations on the amazing leap (through sheer brut force effort and commitment). To go from 420 to mid 600's is already an remarkable achievement. It's great that you still have the energy and commitment to make the next jump to the 700+ club.
I'd be happy to look at your ESR but I'd like to get you thinking about a key area to focus on that you may not have in your prep until now. That's your in-test process in quant and verbal. The repetition of practice problems, solutions and practice tests is the core grind of prepping for the GMAT. But now, as you're trying to reach the elite score level that less than 5% of test takers achieve, it's time to broaden your approach to remove ALL the obstacles to reaching your target score. Knowledge of the content is one part but how you apply that knowledge in a testing situation is another.
Let me elaborate a bit on what I mean by in-test process:
In quant, there are 4 key stages of tackling a quant problem: Capture (incl Preprocessing), Visualization, Setups and Execution.
Each of those stages is critical and need to be mastered as a separate stage of solving a quant problem. It may be only 2 minutes per question, but these stages are still very discrete and important. When you have gaps in any one or more of those stages, there's an impact on a large portion of the questions you face in each section of the test. You put up barriers to capturing the full score value of your months of study.
So what's the right plan?
Observation and assessment of your in-test process. It's something that you can try to do on your own but obviously works much better with an experienced and effective performance coach. It's no different than trying to coach yourself to improve in a sport (no so easy to watch your own golf swing!).
By identifying which stages you're falling short in, you'll give yourself the change to create score leaps in a short time (weeks rather than months).
There's a parallel story on the verbal side. I'm to discuss your ESR and assess your core skills so I can provide you with personalized guidance on the next steps you need to take. Message me if interested.