Can I pursue M.Com from Calcutta University and B.Ed through distance simultaneously?

Most places do not offer B.Ed in distance and Calcutta University has recently tightened rules regarding attendance. You can do the courses simultaneously if you find a course that suits you. It will be taxing certainly but might be worth your time.

No, B.Ed is a practical subject so you can't pursue it through distance. You need to be regular in pursuing and it also depends on the college.

Yes, that is definitely possible and it will help you to save time.