NIT

It is not an NIT and IIIT, though. It can be said a GFTI as it was opened prior to Independence by government funds and a few organizations of Bengal.
Moreover, this institute is considered as an institute of national importance and it is mentor institute of IIIT-Kolkata.

Hello, Your rank is quite good. Roughly one fourth of 12K vacancies are reserved for OBC-NCL. So, up to rank of 3K admission is assured. But do not worry. I am attaching a link that will predict college for you. https://www.shiksha.com/b-tech/resources/jee-advanced-rank-predictor.

You can apply for private or autonomous campuses all over India. For those colleges, NATA is not needed.

Yes, you can expect a seat in any of the NITs. Warangal and Raipur are having more chances.

Hello,
I hope you are doing well. Not sure but You can check the list of colleges including NITs and IIITs that you can get according to your marks and rank. Use Shiksha JEE college predictor:
https://www.shiksha.com/b-tech/resources/jee-mains-college-predictor?utm_source=connect&utm_medium=CR_JEECP&utm_campaign=7489993.

If you have a deep interest in aerospace, then only go for it because in this, you have to read higher level maths, physics, computers and many other things. It is also quite boring. Also, for placements, you need to do very well in your academics. You will get a government job in this. This is also a specialised branch. Taking core branches is quite good and also placement-wise. It is also quite easy with respect to aerospace engineering. Follow your interest and dream. That's more important.

Use the following predictor:
https://www.shiksha.com/b-tech/resources/jee-mains-college-predictor

Yes, you are under 1000. You'll get CSE in any of the NITs as most of these rankers go for IIT's CSE and ECE and you have category too with it. I would though suggest you to push for NIT - Trichy, NIT- Allahabad, NIT -Surathkal, IIIT - Allahabad and IIIT-H for CSE, NSIT and DTU. These are the best colleges for CSE in India which you can get through JEE Mains.

Yes, huge difference is there. IIT is the best then NIT, BHU and then Central University and Amity.

On the basis of your JEE 2 RANK. you can apply for the counselling of NITs, IIITs and GFTIs on:
josaa.nic.in
From 15 june 2018.
You can also check the previous year's cutoff's for NITs,IIITs,GFTIs on the basis of your JEE MAIN AIR,
ON
jossa.nic.in
there you would get an idea of your selection.
BEST IF LUCK!