B.Sc Maths

Yes, you surely can apply for a job in defense services once you complete B.Sc Mathematics.

Hi Dhiraj!
You should contact the college authorities for the same. They will be able to guide you better in this regard.

Its quite difficult to find yourself an 'A grade' college under the AEGIS of DU but you may try.

You may try. There are chances you may get in with OBC quota but in my opinion, do apply to other colleges and don't just risk everything on Fergusson as 80% is not a very good score for it.

See a degree like B.Sc. Mathematics does not prepare you to work in corporate sector but due to good rankings of some colleges like Fergusson there happens a campus placement and students get job based on their skills and resume. So the students who get placement due to their hardwork and efforts, get an average package of 4-6 Lacs per annum. And for the type of job it can be in field from finance to HR to analyst.

Hello dear, after completing your B.Sc. In statics or economics
you are eligible for M.Sc. Or other master courses in same feild.

Any degree that you do adds to your competence as well as strengthens the job claims. In you case, if you are already working with M.Sc. And B.Sc. This will enhance your claim in Higher Education. I suggest that you should do B.Ed that will be more beneficial for school teaching careers.