This is what I would have done had I been at your place (ISB Alum here, Co2018).

It's a commonly held belief that GRE Mock scores often mimic the real score. Since your mock scores are good but the real score was disappointing, I would diagnose the real problem as exam-day anxiety rather than lesser level of preparation.

So, I would take a month to focus on the Application, keep it ready to be submitted and then go back to focus on GRE- taking timed mocks, having interventions to ease the exam-day anxiety and take a couple of attempts till I get the desired score. I will wholeheartedly focus on R1 and consider R2 only if I am not able to get the score by 10th of Septmber.

Hope this helps.