1) If you have above a 3.0/27 as an undergrad, your chances of passing boards aren't much different than anyone else who might have higher stats. The reason admission is competitive isn't because lots of people aren't capable of passing boards.
3) You get second chances to pass. If on the re-take(s), where you have that much more time to study for it you still can't pass(note this isn't the MCAT with abstract verbal passages some very bright people can't hack), the field of medicine simply one that isn't for you. Keep in mind even failing a board test a second time isn't often enough to drop out; you get additional chance(s) after that.