That is a grown ass man. The least he could do is say a few sentences at family gatherings. Being “a man of few words” doesn’t excuse embarrassing your wife. SPEAK UP
I mean, we have no evidence that he's ever been different. No one has any requirement to conform to anyone else's expectations on the right amount of social engagement.
If the person you're with is like that and it's the sort of thing that is gonna cause you to run away from them for weeks on end, maybe don't marry them instead of expecting them to change. It doesn't seem like this is some foible that appears from time to time - it sounds like he's basically always like this. You're basically saying the man should change his entire persona after decades of marriage because otherwise things might be a little socially awkward in certain situations.
I could never be happy in a relationship with the dad but if I found myself dating someone like him, somehow, I'm going to break up with them, not try and convince them to change.