Engineering

It would be difficult for you to get civil aviation. Visit the following link
https://www.shiksha.com/college/birsa-institute-of-technology-bit-sindri-Dhanbad-36789/admission
also see AFCAT exam.

You have to clear backlog otherwise you cannot study in B.Tech. The only way left is to use your 12th score and sit in entrance exam JEE or other exams. You can go for private university, if possible to pay the fees.

Take the leap towards the next stage of your career with programs that have been thoughtfully designed for working professionals. They are structured and scheduled to allow for a fulfilling work life & study balance. Depending on the need and depth of upskilling, students have an option to choose from specializations within following: Certificate programs, Diploma Programs, Professional Programs, PG Diploma Programs and Master Programs.

Dronacharya College of Engineering is private campus affiliated from government. University MDU, Rohtak and approved by AICTE. You will get the government. Degree of MDU University after 4 years.

If you are interest is neglected then you should join ECE, because it is well established in NITH whereas Material sciences are recently started. But, if you have interest in material Science then you may go for material Science. ECE-70%
Material-30%
Best of luck.

You can check the opening and closing ranks of round 5 for various categories at
https://josaa.nic.in/webinfocms/Handler/FileHandler.ashx?i=File&ii=173&iii=Y
It includes all the courses and institutes.
BEST OF LUCK.

Near Delhi I can suggest. I have heard a lot of good things about Thapar Institute of engineering and technology. They are the leaders in Engineering based courses. Ver renowned for the same. Their admissions processes are still open and will closing soon, so hurry up if you wish to apply. To know more visit - http://www.thapar.edu/.

Yes, you can go for mechanical engineering after 10th, but only in the field of Diploma & ITI in ME.
After that, you can pursue in B.Tech in ME by lateral entry scheme direct admission in the 2nd year of B.Tech graduation.

Please don't be disappointed, you have 74.4. You can try for colleges with your rank on last year opening and closing ranks. You also try for GFTIS and also your state level college.