As usual most things outside of the very narrow window of JW content he is going to have a hard time with because he has to think of someone other than himself.
That's really it, isn't it? It's obviously a huge issue for him and that's all he really thinks about. How can I attach myself to this joke? After all he included it in his 9 grievances against WT. Let's take an unscientific "survey" here. Think back to when you were a doubting JW, would the masturbation ban had made the top 9 on your list of things wrong with the organisation? The prohibitions regarding sex would, but I would have rolled it all into one generalised bullet point. Mine would have been:
Prohibition against certain kinds of sex
Disfellowshipping of ones who commit fornication. (I say disfellowshipping, I wouldn't expect a church to condone it)
Prohibition against marrying/dating/having sex with ones outside the religion
I would have rolled that all up into a single entry: Policing one's sex lives. Masturbation would have been included but I wouldn't have thought to mention it directly, especially the way he did as a sole bullet point. Masturbation is really a victimless and unreported crime in the JWs. For reasons which are obvious it's very easy to get away with and generally people did. I don't get why he's so vocal about it. The only way I can rationalise it is that he considers it an essential part of his sexuality.
Well, if we are to believe the Dijana leaks and his livestream, this is really what happened especially after the birth of his second child. His sex life consisted of three things at that point: masturbation, porn, and sex workers.
Evans might be able to learn the craft. I tend to doubt it, mostly because he cannot laugh at himself and he bristles at any kind of criticism, which he would need to heed in order to improve. I just can't imagine someone being good at comedy if they cannot laugh at themselves.
Think of Eminem's act. Had he come out in the late 90's dressing like a gangster, rapping about money, women and street violence, he would have been laughed off as another incarnation of Vanilla Ice. Instead, he dyes his hair straight blonde, dresses like anyone attending a rap concert would and raps about his mum being a drug addict who lived in a trailer, his wife cheating on him, his fleeting and unsuccessful romance with Mariah Carey and generally how dysfunctional his life was.
To even have a chance of his wanking chronicles working in front of an audience, he'd have to devolve to that level and go into how unlucky he was with women before going into all this. Even then, you only want to make perhaps a fleeting reference to it. And as you said, you need to have an entertaining way to deliver it. This is not easy to do. And I don't think he wants to do this or even thinks this way. The methodical way he just lists off the sexual taboos of JWs is what really lost him the audience for good. It wasn't funny and by this time he was just preaching to them about his activism.