Hiii

Your expected rank will be around 6039. The score of 99.3093570 percentile is a quite good score. The cutoffs for NITs are yet to be released so i can not exactly say whether you can secure a seat or not but as per the previous trends, you have a great chance to get into NITs.
Talking about IITs, the admission to IITs is not depending on JEE mains. For IITs you need to qualify JEE Advance, and as per your mains score, you will surely be eligible for JEE Advance.
Still for the confirmation we need to wait for the final results to be declared.

Hope this helps

Thanks!!