I agree that the line would not be about marriages, however, Shai's interpretation makes most sense to me:
Regarding the prior discussion of "me and you, we're three and two" might have another meaning. In baseball, three and two (or better, 3-2) refers to the "count". That means that the hitter gets a free pass to first base (base on balls, or walk) if he doesn't swing the bat at a bad pitch out of the strike zone. If the hitter swings and misses, or doesn't swing at a good pitch is the strike zone three times, then he "strikes out" and that counts as an "out". A "full count", when the count is 3-2 means that the next pitch will result in either a hit ball, or a strike or walk. That's why they call it "the payoff pitch", since something has got to happen!
So I think that fits in perfectly with the rest of Mark's line, "something's gonna happen now, it has to".
But as typical with so many of his lyrics, there are likely multiple meanings. My gosh, even something as simple as 'me' and 'you' having three and two letters.