There’s always Kinsey, although I’ve always been distrustful of his reports, at least as they pertain to the average American man and woman of the time. The main problem with surveys based on detailed questioning about sex, especially in the 40s, is that the sort of people who would agree to participate would not be representative of the population as a whole. Kinsey drew sweeping conclusions about the sexuality of Americans based on answers submitted by those Americans who would agree to respond to intrusive questions on their sexual practices. That would have been a small minority in the 40s, and I think it highly probable that their open attitude to sex, as reflected by their participation, would make their experiences and habits very different from those with more conservative attitudes.
In short, Kinsey really found out only the sexual habits of people who take part in studies on sex.
That can be a problem with all types of surveys, but especially so in this case. An involuntary sample is basically needed to make a survey sample representative (any other type has self-selected sample bias). Which means calling up random people across the country at their homes to ask them about their sex/masturbation practices. Good luck with that.
There was a lot of criticism of the Hite report for the same reason, and that was more anecdotal and much less scientific than Kinsey or Masters & Johnson.
You’ve asked me to give a list of employees broken down by sex and age. I’m sorry, but I can’t do that. We have no one broken down by sex, though we have two broken down by alcohol, and one broken down by overwork. Our people always retire before being broken down by age.
Are there periodical-type journals that a university library might have that you could look at? One of them might have a study. Or if you have a large hospital nearby, their library might let you have access if you’re doing genuine research. Surely the appropriate professional organizations have journals that print studies like that.
A quick perusal of PubMed (a NIH service) yields this: Sexual Behavior Later in Life. Masturbation is only a small part of that study, but it may give you a little bit of data.
I doubt you’re going to find one study that encompasses all the points you’ve made in your OP, but you may try digging deeper into PubMed or looking at the table of contents in various human sexuality journals.
If you can’t access the journal, I can excerpt a little data, but PM me.