Your GPA is below average, and current GMAT score of 640 won't be enough to make up for it. Though you have valid reasons for your low GPA, and you proved yourself in the repeat courses, still 700+ score would significantly increase your chances. You have notable achievements in research which is going to be a plus point for your application.
Your work experience is on the lower side. Even though there is no set criteria for work-ex, most schools require the students to have at least 3 years of experience. The quality of your experience at the start-up seems to be good.
You have not mentioned anything about extracurricular activities. They are quite important in application.
If I were you I would wait for two more years, and have quality work experience and extracurricular activities on my application. This would help you in writing stellar application essays. You should also decide on your post MBA goal, and how an MBA fits into your career to help you achieve that goal.