I suggest u give improvement exam, because u are very close to 75, since syllabus is same, it won't be a time waste, plus u will get chance for iit and not in drop. So Imo improvement exam and preparation is best option for you. Don't hurry to take a college, good college late is better than bad college early. Give improvement and take drop

But I mean, u are already prepared 72 percent even if u have to give all. Could be lil hard, but it's worth a shot. Because obviously even if u fail to get 75 u would have done some extra practice, it would not be a waste. Plus the opportunities it brings (if ur marks get better) are much greater if u somehow perform well in mains or advance. I would have given it if I was in place of you. Good things don't come easy