M.Sc

Eligibility for M.Sc in chemistry is under graduation in B.Sc with chemistry as one of the subjects, and maths as one of the subjects at 10+2 level. The minimum cut-off at undergrad level is 55% for general category and 50% for the reserved category. Candidates would become eligible for admission in the IITs after clearing the IIT JAM.

To pursue MS from a foreign university, you would first need to clear your backlogs, unless mentioned otherwise. Your work experience and scores in GRE are fine.

The eligibility criteria for M.Sc is a minimum of 55% marks in B.Sc and a good rank in the qualifying examination.

That depends on the university you are applying to. Few universities have minimum 60% as the cut-off while others have 50% as the cut-off. For eg: DU has 60% as the cut-off, whereas, Manipal has the 50% as the cut-off.

For IIT-JAM, the eligibility criteria is 55% in UG.

As per me, Indian Statistical Institute is the best choice for you.