IIT B.Tech, Machine Learning Lead, 14 years work ex, 3 patents filed. Planning to switch. How much fixed LPA should I ask for?

Apply data science to the problem. 😄

Ask salaries of some of your IIT seniors or batchmates, working in similar profiles, and calculate some measures of central tendency (such as mean, median, mode), and then safely ask for a bit more than those amounts 😉

You can easily get 1.2-1.8 Cr CTC. Fixed can be between 80L-1.3Cr and variables(Bonus/Stocks/ESOPs) depends on the company.

Even then I would suggest to see levels.fyi to see the salaries of equivalent positions in top companies.