So many people go on and on about Anne being a cheating whore. But the fact is, Tony is far less transparent about his liaisons than Anne is ( that is if you choose for him to have sex with other people). Yes Anne cheats, but eventually she owns up about virtually everything ( prior to them both clearing the air whilst on holiday). Tony on the other hand, keeps silent about virtually all of his cheating, and in his case it's far worse, because there's no arrangement for him to have sex with other women, when Anne isn't present.
Having said that, they do eventually own up to everything they've both done behind the other's back, whilst they're on holiday in Barbados, and the implication is, that in future they'll both keep the other person informed of their activities. So it seems at that point, that the cheating phase is over. Whether that will happen in the reboot I don't know? We still have quite a long way to go, before we reach that point in the game again.
For me, a real turning point in their relationship happened, when Anne confessed about what she'd been doing with Martin. That of course depends, on you initially choosing for Anne to cheat with Martin, and then later for the MC to find out about it, by sleeping with his ex-girlfriend Emma (ironically, the MC can only find out about Anne cheating on him, by cheating on her himself). I think the scene that follows, where Anne tells the MC about having sex with his Dad behind his back, was one of the hottest in the game. Because Tony is at his most aggressive and dominant with Anne, when she talks about having sex with Martin. This is pretty much the time, where him and Anne start fucking more often.
Considering, that he's seen so many times, that Anne likes it rough and loves being totally dominated. The MC seems unable or unwilling to replicate this, except on a few occasions. Which seems really odd. I mean why wouldn't you do something that your partner obviously loves? Tony seems to have no problem being an alpha male with other women, so why not his own wife?