So as a writer myself unless your selling your product to make a profit, focus on the story that GETS TO YOU. Or turns you on. Or interests you. Especially for a first game, because that motivation will drive you through the development phase. If your making a game for other people, then making polls is great because your using it as a metric for what your audience wants but again - who and why are you making this game for?
With Marina I've literally gone through 4 scripts, only one of which really catered to diverging paths for every type of NTR fan. For example in one I had her totally become a cheat and throw it back in Kenji's face (because he started her on this path) and even another path where Marina lets Kenji fuck other women in front of her - yes both worked but these felt so out of place in my general story as to deserve their own games - which brings my point around to this - even a short game takes time and if your not enjoying the story your crafting it around your going to lose interest or become distracted by a project that is more "you". So focus on the story you want to tell, be damned if it pisses other people off and do that. Especially for a first game.
If I wanted to write a story/game where Kenji and Marina join an S&M club - and that idea pisses off a bunch of people does it really matter if they are all getting it for free? I would say focus in one that story and develop it as best you can, so even if they don't like the themes when they play it they can still say it was a GOOD story for the theme. And that theme needs to be something YOU want to work on. Again unless your trying to sell it for money, but most early developers like myself are just trying to get something done.
As for diverging paths, do what I did. Write your main story, if you SEE a point where the story could allow other options simply NOTE it at that point and continue writing the main story line and "true ending" (or as you see it). I didn't do this the first time, but learned my lesson from it, that by focusing on that central story it allows you to go back and better develop those other paths once you have the basic story finished. If you develop each little path as you go, your story will sprawl and by the end ir won't have a clear path forward. Or at least thats what I learned.
Now for the ending - my suggestion for NTR is write it first or what you want that ending to be. IF you want the ending to be "wife is fucking neighbor and never tells husband, husband enjoys knowing that she does this and knowing that he knows she doesn't know he knows (LOL) then you have the basic plot to which you develop your story to its end. For NTR plots this really DOES help a lot.
Good luck!