JEE Main

There is no specific answer to this there is nothing to do with JEE Mains rank for the rank in JEE Advanced A good rank in JEE Mains can't get you a good rank in JEE Advanced It depends on many aspects like difficulty of the exam, preparation by your son, his dedication, clarity of concepts, the study material and coaching/Institute he has referred for the JEE Advanced exam.

If you are getting more than 1 Lacs rank it will be quite hard for you to get admission in DTU or NSIT. But still try your luck as there will still be some seats left for you to grab.
All the best for your admissions in them just try your luck. Upvote if you liked my answer.

For getting a seat in not the percentile should above 96 percentile, so he cannot get a seat in Nagpur.

Your JEE Mains mark were good but as you failed in Maths, then you should study first for re exam. Then you should think about opting for colleges.

You should definitely enquire about admissions to DIT University.
Link: https://www.dituniversity.edu.in/#

There may be chances of getting a seat in IIT Kharagpur, according to your JEE Mains Percentile there may be chances of getting a seat.

JEE Main result will be declared on 31st January 2019 (for 1st session) and 30th April 2019 (for 2nd session). JEE Main 2019 counselling process will be started from June 2019.

According to your JEE Mains Rank, there may be chances of getting a seat in new NITs.

No, they don't look up to JEE marks for the lateral entry. You will have to get the qualifying grade and clear the cutoff provided if not then you need to appear for lateral entry test.

Yes, you will get chance of getting admission in other NIT's.