A few comments about the potential 'sharing' with D in this game.
Firstly, I find it a little odd that people are offended that F might get cucked. If you knew F in real life, you would think he was a creepy depraved pervert who probably should be in prison. So I would have thought you would be happy he gets cucked. But it's a porn game with porn rules so w/e.
Secondly, I play this game because I think D is hot. And I like watching hot girls getting lots of dick. Sex with F is fine, but it gets boring real quick. If I had my way she would be getting gangbanged but that's my fetish. The more D explores sexuality the better. The titillating taboo of sex between F and D is done. It's time for either D to go full sex-goddess mode or just end the game and they live happily ever after.