JEE Scores

Yes, they will accept JEE Mains score.

First believe that it's doable. The first prerequisite is however that you at least have the basic knowledge of about 60% of the syllabus. Rest, one month can be devoted to rigorous revisions, solving previous year papers with a time constraint and attempting regular mock tests. Practice is the key. And time management is the way.

Yes, absolutely there is a chance to get a government college in West Bengal. Do proper counseling and be updated. You can take help of Shiksha to find your specific college.

To get into IIT Madras, students need to pass the highly competitive Joint Entrance Examination JEE Advanced, and the minimum marks required for admission varies each year depending on the difficulty level of the exam and the number of available seats. Generally, students who score in the top 2,50,000 ranks in JEE Main are eligible to appear for JEE Advanced and admission to IIT Madras requires a very high rank, often within the top 500-600 ranks in the JEE Advanced exam. Students must prepare well for both JEE Main and JEE Advanced to secure admission to IIT Madras or any other IIT.

No, you cannot get admission because cutoff for OBC is 74 percentile.

You can get admission in the following colleges:
RK University,
The ICFAI University, Jaipur, Brindavan College,
Dream Institute of Technology, Gandhi Engineering College

It's always better to enter JEE percentile, to gain more attention in forms, but if your percentile is less, and is not required to mention, then don't.