Indian Institute of Social Welfare and Business Management

University of Calcutta is very strict in marking scheme. Getting 70%+ is a bit difficult in University of Calcutta.
However, if a student studies properly then getting 60% will not be a big problem.

The conversion depends on your CAT %ile, work experience, GD PI WAT performances, academics, extra-curricular activities, etc.
A CAT score of 80%ile with decent GD PI WAT can help you to convert.

IISWBM does accept MAT scores, only CAT scores are entertained.
A CAT score of 75-80%ile may fetch you a call for GDPI, after that your profile academics, work experience, may take into account.
GDPI call are done solely on CAT %ile basis and no profile based calls are done.

75-80 percentile in CAT may fetch you a call for GDPI.

Yes, you need to apply via your Diploma certificate if you want to join Data analytics field. Use your graduation degree where graduation is mandatory. It will also add value to your cv. There are many vacancies in IT firms where knowledge of data analytics are required.

The course you've mentioned is a 12 months course and has been into existence from 2015. There's also a full-time MBA (Day) Course (2 Years) affiliated to CU, with Business Analytics & Systems Management as specialisation. Placement in MBA (Day) Department is good with top recruiters for BASM being Kantar IMRB, Nielsen, ICICI, etc.

Going by the trends of 2017 CAT Results, you do stand a chance of getting a call from IISWBM, your chances are more, if you have industrial experience. All the Best.

Going by the trends of previous year (CAT 2017), average CAT percentile who got admitted to IISWBM for MBA (Day) 2018-20 Batch was around 75 %, but there very few are students with 65+% in 2018 Batch. Since you have industrial experience, you have moderate to good chance of getting a call from IISWBM for MBA (Day) programme.
All the Best.

IISWBM does not accept CAT score. Kirloskar is okay, but it's placements are not up to the mark right now. I can't comment on ISME, as I don't know about it. NDIM is good. You can go for it, if you can afford their fees.