I don't know it was that successful until I check Box Office Mojo. The last movie grossed only 623m while this movie almost reach the 1 billion mark after 3 weeks
But that's completely who Tony Stark is. When it comes to Pepper and life's decision, he is thoughtless, that was Pepper's job to take those decisions for him. That's like him saying to Pepper in IR1 that she was ALL he has and then sleeping with other women. Or trying to make Pepper his girlfriend, almost kissing her even and then flirting with Natasha Romanof and countless other women in front of her (BTS).
Yesterday, 'Iron Man 3' became the 16th movie to reach $1 billion worldwide. At its current pace, it should wind up ahead of 'Transformers: Dark of the Moon' ($1.12 billion), which will make it the fifth-highest-grossing movie ever... >
It isn't really a plot hole if it's acknowledged in the movie and in this case it is; he acknowledges outright that the decision you're referring to was a stupid one and it's one which intentionally reflects on his character, not one which was the result of sloppy screenwriting.
