You are in no way forced to do the scene with the demon. IIRC he doesn't even have a bad end when the choice is given to have the sex scenes. And yes, all scenes with the demons result in a bad end when you climax. You are warned of this in the text. And even if you pick a bad end you get the option to re-do the choice. You can also press "W" at any time to open a walkthrough to learn the right choice.
To the "punished and shamed" the creator has made it clear that the game is not supposed to judge anyone, but it is also a comedy and the main character is made fun of. This is something you have to deal with.
To the lack of assertiveness: the story is plainly set up that the MC is powerless and sexually repressed in the beginning and surrounded by people that take advantage of him. Generally if you end up with the choice to be alone with people, they will make a pass at you, sometimes you get an option to back out, sometimes not.
To top/bottom, the game overall is pretty balanced in that regard, most "dedicated" scenes offer choices regarding the roles. But some scenes are fixed because of story reasons.
