These are all examples of 'might have'. We use 'might have' to refer to hypothetical situations which could have occurred in the past... but DIDN'T. For example, #4: You didn't study at that university, so unfortunately you didn't become a good surgeon. You can't use 'may have' in these situations. 'May have' and 'might have' are used, more or less interchangeably, for speculations about the past when you don't know what happened. For example: The death of Marilyn Monroe is a mystery. She may have committed suicide or she may have been murdered ---> These are speculations. 'Might' or 'may' is possible here. If Marilyn hadn't been so beautiful, she might have had a happier life ---> We are talking about something which we know didn't happen, so we can only use 'might have' here.

Where I live we use "might "much more than "may ". I live in the Midwest of the USA Aroung here the use of "may "is pretty formal. I am not a English professor so I might be wrong when I use it

1.- May it is used in formal context. 2.- May it is more probable than might

May have has a higher likelihood of happening. Might have is less likely to have happened.

1 you........ told me there was a policeman behind me! 2 why did you drive so fast? you ...... died! 3if you had listened to me you ...... lost less time and money 4 if you had studied in that university you..... become a good surgeon