Jee main 40 and 80

Advance 20

Considering your scores for the previous attempts, there has been improvement in jee mains score. That may improve more a bit but you might still not get a NIT.
Considering the score for jee advance it's very difficult to get IIT even in the next attempt.
So I'll suggest you to think once again before taking a drop. You can try for state govt engineering colleges with your jee main score or you can get private ones.

In my opinion it's better you don't take a drop and utilize your one year in college itself.
All the best!
Feel free to ask further doubts.

My score is 78.524 percentile.