M.Com

You can do B.Ed, as you have secured 55% marks in graduation. For B.Ed, minimum 50% is required.

I assume by management seat you mean general admission. If so, the eligibility criteria would be 50% in all semesters of your B.com. if you are eligible you can apply for the course online. You may refer this link for guidance as to how to apply.
https://christuniversity.in/commerce-and-management/commerce/master-of-commerce-(mcom)/860.
There would be a selection process that you need to clear after applying. The selection process consists of skill assessment (skill assessment will consist of a test on written skills, communication skills and logical reasoning.) and personal interview.

Yes you can. B.Ed can be pursued after any graduation/ post-graduation degree.

You have completed your graduation and Masters in commerce. Definitely, you should have enough command in your subject. It will be more convenient to you to apply for commerce subjects. But, if you have enough confident in English, and you think that you can carry the subject, then you can apply for English subject.