IIT Kanpur - Indian Institute of Technology

Both are better but IIT, Bombay gives better placement than IIT, Kanpur. The infrastructure of IIT, Bombay is also better and it is listed in top 10 universities of India.

You cannot get admission in IIT on the basis of JEE Mains, but clearing it is an eligibility criterion for taking JEE Advanced which is the exam for getting into IIT.
For JEE Mains, you need a minimum of 100 marks to stand a chance, but you are still not in the safe zone.
As every year the cut-off revolves around 100.
For Advanced, the max. rank to get IIT-Kanpur or Kharagpur is 30K to 35K but then too you have to compromise with the branch.

After getting a call, the selection process would depend mostly on your GD-PI performance and since you seem to have decent academics in 10th,12th and graduation above 6 so chances could prove favorable for a conversion. So please give emphasis on your GD-PI preparation now.

You need to get rank under 1000 - 1500 to get admission in any of IITs.

Government institutions do not accept donations and especially IITs do not allocate seats based on donations.

The criteria for applying to IITs vary and for IIT-Kanpur, the criteria necessitate the candidate to have at least 85 percentile in CAT to apply for MBA.