While there is a bit more content on the sharing path, it's usually just one or two scenes and some dialogue. Week 3 has an alternate scene depending on your path. The sharing itself is mostly facing the reality that many of the women in the game are married and do, believe it or not, have sex with their own husbands. It will stray from that however, but most of the time when it does it will still stay in the family, so to speak. One of the girls has their parents show up and well.. the game does indeed have an incest tag...
As for sex without the mc: it has happened with a certain husband and wife, but there won't ever be a time that the mc gets cucked or simply watches. Also the golden rule of the game is that the mc will always be the first man to have sex with any of the women on-screen. (It would have to be assumed that the married women with kids have probably had sex with their husbands at some point in time off-screen). For the most part, the sharing will be with husbands/brothers/sons/etc.. I think you may be able to figure out what my main fetish is.
As for incest with mom.. it will happen, but maybe not for a while. I want a bit of a bigger payoff for that one, tbh. There is, however, plenty of naughty stuff with her already and that will continue for sure.
Each episode is a completely different upload. I don't reuse any renders, so if I didn't make each release separate the file size would be insane. Hope this answers your questions!