JEE Main

I will prefer you to try TMH for scoring good in maths.
But the main thing is to go through previous year JEE questions which will give you an idea and many of the questions will clear your misconceptions.
GOOD LUCK

Hi.
Necessary Marks depend upon cutoff but Computer Science is trending branch so its closing rank is lowest for every NIT. So, you should score minimum 200 for CSE.
GOOD LUCK.

CSE is the best engineering, but I will suggest that you choose the branch according to your interest. If you are interested in programming languages then opt for CSE.

You can surely get admission in new NITs and SRM.

http://www.bitsadmission.com/bitsat/BITSAt_2017_Brochure.pdf
Check this link for BITSAT syllabi.

It would be little difficult because you need speed for the JEE examination and for that you need to learn short cuts and various tricks, even if you want to self-study, then enroll for mock test papers and online tutorials of some good coaching institute.

For NITs and IITs you need 75% + but there are some low colleges which expects less percentage. Go to shiksha's website and find colleges with less eligibility marks.

JEE Mains cut-off trends:
2017-81 marks
2016-100 marks
2015-105 marks
2014-115 marks
2013-113 marks
Anything above this you should qualify for counselling in govt. engineering colleges. As competition is fierce, you should secure high marks to qualify for the merit list of the top NITs.
Here are the most important factors that help derive JEE Main Cut off each year:
Total number of appeared candidates
Difficulty level of exam
Previous year cutoff
Number of available seats
Overall performance of the candidate

It depends on how are you preparing each subject. Yes, giving your 100% in all the three subjects you will top the JEE Mains. Try to do self-study for 6 to 7 hour per day. All the best!