Sir reading some info, i guess i cant tell any number blindly without test.

I think
I can first try to give these values

max_children = 100
start server = 34
spareserver min and max = 20 & 50

We have around 20GB free Ram all the time. Why can't we use it for php-fpm?
Are those values safe to check?

But max_requests, why should we limit the numbers to 500 or 2500? Why cant we have unlimited? What is wrong in setting it to zero?