<aside – I got bollocksed for going for fools mate in a competition, when I was in primary school, apparently it was unsporting. The prick who ran our club stepped in and made us reverse the move and play on, and I ended up getting humped and put out of the contest entirely. In short, I can’t give much advice on chess but there’s nothing I don’t know about carrying a petty grudge for 30 years.>
How into the theory side is he? It turned out I had a good intuitive feel but I no patience for sitting and learning about the game, so I never amounted to more than just a really good half-assed player, I never became even a really bad proper player. I couldn’t even be bothered to learn openings, it took all the fun out. It seemed to me, and still does, that it’s basically a different game when you play it with the deeper knowledge, but that takes effort… And you probably need to be quite a different person or at least happy to play in a different way.
If in doubt, respond to everything he does with an arched brow and say something like “Ah, the Ballsteiber Inversion- you don’t see that much these days”.