Some of this advice is about addressing rules and some is about not letting crap in life bother you. Take it for what it's worth.
When I play someone I've never played before, I try to assess the situation/person. If the rules are in question, don't put yourself in a situation where there is something on the line - like money, your health, or pride. You knew this guy was going to be an issue the minute you laid eyes on him. You can always just choose to understand that there is a very good chance that you will never be on the same page with the guy in front of you. Accepting that, you can just go with the flow. I mean if they don't normally play by your rules, then they won't be very good at absorbing the whole ball in hand thing, so I don't usually try to teach guys like this something new. Sometimes people are just hot heads. Not that they are trying to cheat, but they could believe they are actually right and not be trying to see it from your point of view because they have no clue that there are other ways to play. They just get mad too easily. Other times you meet locals who respect how well you play and when you tell them the "real" rules that they have never heard of before, and let them know it's how the pro's play and it's an international standard, you are opening up a whole new world for them, and they like it.
So when I'm playing with someone new, I'll ask if they play in a league, if they are familiar with valley, BCA, "Ball in Hand" rules or play the cue ball from the kitchen after a scratch. At that point you will have a very good idea of whether they play by the rules that you are used to or not. If they play from the kitchen, then you don't need to worry about 90% of the rest of it.
If you do get into a point by point discussion about the rules, try to get it all hashed out before you start. If they say something like, "it's straight eight, everybody knows what that means" then they either don't understand that there are a lot of different ways to play, or they are intentionally setting up a "misunderstanding". At that point you have to say something specific that will most be likely be contrary to what they normally do, just to get their attention and force the conversation, "So if I scratch on the eight, then I don't lose right?"
I have a list of seven things I try to cover before hand, and this is in order of importance (in terms of figuring out if you can get on the same page with them or not). If you can't get on the same page, just do it their way, but don't bet. Or lose a game as quickly as possible and go to a real pool hall...
1. BIH rules or in the kitchen.
2. If they say in the kitchen, ask them if they consider safeties "dirty pool".
3. Table open after break or take what you make?
4. Call shot or call pocket?
5. Eight on the break is a win?
6. Scratch on the eight is not a loss?
7. If you move a stationary ball, put it back or opponent's choice? (also cover that touching a moving ball is always a foul).
I will often ask 5 and 6 earlier just to feel them out.
Even if we are playing their way I will try to talk them into playing my way on two points. I want...
Table open after break, not take what you make, and
Call pocket, not call all details of the shot.
As I was saying above, if you accept that you are playing by rules that you are not used to, you can just chug along and still have a good time. Just go with the flow. But this guy was changing the rules as you go. That's more difficult. You said you had a purpose. You wanted to see how good he was. So you have to take solace in the fact that you achieved your purpose. I would think of the rest as inconsequential. Best you can do is make your exit and let him know that you're not willing to play with someone who likes to make up the rules as he goes.
Fatz