Hii

There is no official announcement about the cutoffs for admission into NITs, Once the cutoffs are released you can check whether you are eligibile for NIT or not. As per previous year cutoffs, you do have some chances of getting NIT.
Talking about JEE Advance, to be eligible you require to have around 80 percentile in Mains. So yyes you will be eligible but to be sure you are supposed to wait for the final result to release.
Also you can appear in April session of JEE Mains and try to score higher than this score. You need not to worry because even if you score a lower grade, best of the two will be considered for future process.

Hope this helps
Thanks!!!