To answer your questions:
(1) Yes. Sure, if you're at 680 or below, you can still get in (10% have scores below 680) -- but it's not because they're amazing applicants - they're LUCKY (plenty of others who are also amazing got dinged as well, even with 700+ scores). Anything below 700, and you're gambling.
(2) Yes. There is no real difference between rounds 1 and 2. Yet, year after year some applicants microanalyze the differences between both rounds.
Retake the GMAT and apply in Round 2.
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