B.A English

First of all, Mumbai University does not offer BA honors in English. As far as national reputation concern, u fortunately there isn't any colleges in Mumbai except St Xavier's. You may look other as follows:
1. Mithibai College, it has a department of English
2. Ruia College
3. St Andrew's College
4. Wilson College

Yes, you can pursue MBA after completing UG in any stream.

You can go for certification programmes wherein you require only 10+2 marks.

No, you can't take economics, but you can take English in BA. You are not eligible for economics, because for that you must have math or economics at 10+2 level.

Dear,
With this percentage, you need to check the admission process and eligibility for the particular programme in which you want to apply.
Even you can check the programme wise details on Shiksha website.
All the best.

GD Goenka University has a dedicated School of Humanities & Social Sciences for BA English (Honors) programme. The English department's faculty of GD Goenka is really amazing with good academic & working background. GD Goenka University also offers inter-discipline learning. You can go ahead for GD Goenka University.

You may refer to the following link for the list of top colleges for pursuing humanities in India: https://www.shiksha.com/humanities-social-sciences/ranking/top-arts-colleges-in-india/95-2-0-0-0. Majority of them offer BA English.