Humanities & Social Sciences

There is no set formula for employment.
There are no guarantees.
However, choosing Hons. would mean that you will study the subject in great depth, and that might expand your options for your career.
Both English and Psychology have a great scope. You can choose either of the Hons., or you can choose B.A. Gen where you'll be studying both, but not in that much depth as in an Hons. course. If your interest lies in both then you should study B.A. Gen, or if your interest gravitates more towards one of the subjects then Hons. would be a better option.

Science students have this advantage that they can apply for humanities or commerce stream. So you can apply for any course.

Yes, sure you can. But in DU they deduct 2.5 % from the best four subjects percentage if the best four include any other subject than maths.

I think no, because last year the cut off touched 81%.
Also, every college offers different cut-offs for different courses.
You may check the previous year cut off in the below link :
http://www.du.ac.in/du/index.php?page=cut-off-2017

For eco hons, maths is mandate. Even for B.Com (Hons) programme maths is mandate. So I don't think that any university offer eco hons without maths. But, you may try to other private university otherwise the chances are negligible.

Yes, sure. For other details, you may check the prospectus of MA English DU:
http://www.du.ac.in/du/index.php?page=m-a-english

The selection of subject based on best four means you have to arrange your marks in descending order and whatsoever is last don't include in the best four.

https://www.shiksha.com/college/aryabhatta-college-benito-juarez-marg-Delhi-49142/reviews?sort_by=year+of+graduation
You can check the reviews of college and I think you are eligible for political Science. Because last year, the cut-off closed at 86% for general category.
All the best.

Yes, through JAM.