B.Sc

Hello Yash,
If you are planning to take CAT exam, it is a very good decision.
CAT exam has topics related to maths like arithmetics and reasoning.
B.Sc (MPCS) is better than B.Sc (PCM) because, in computers, you are able to know more about the computers and as well as maths. And also computers having a huge scope than chemistry nowadays. Another thing, computers is also helpful in MBA.
I am also a B.Sc in MPCS student.

Yes, that would certainly help you.
Go for the language in which you are interested. Choose a language as per your comfort level.

The minimum requirement for B.Ed is that the individual should be a graduate in any discipline (BA, B.Com or B.Sc) with a minimum percentage of 50% in their undergraduate course. You could try IGNOU or try correspondence courses in B.Ed.

Himalayan University is UGC accredited. However, it is relatively a new university and will take some time to establish itself. If you want to pursue a course through distance, you should be okay.

Yes, you could secure admission in Fergusson College through management quota. There is a 15% reservation for under graduates in the first year. However, many people get through even with an average percentage. There are 3-4 cutoff lists, and you may not have to wait for the 3rd or 4th cut-off list.

Do not get disheartened if you have low grades or even if you have a 1-year gap in your education. There are many like you in the same situation who have risen to the occasion and secured a decent job. Prepare well for the interviews and read a lot about the profile that you have applied for, and I am sure you will get a decent job.