From what I remember, in theory, anything and everything that can cum inside Monica has a chance to impregnate her. However, the "father" of the pregnancy has no bearing on anything from what I remember.
In any case, once she loses her virginity, monsters can rape her in combat even without defeat scenes, and I think there were tentacles monsters too. There may be a tentacle defeat scene too somewhere... but the monster content is very small in this game.
Basically, if your main goal is that sort of content, it's probably around 10% at most? Not worth the effort if you don't enjoy all the other stuff that the game has to offer.