i dont like "full harem" in the sense that everyone is together with everyone, personally i like the solo paths more, but from the 4 endings i played through so far, none had any pregnancy, especially let down by the Valeria path, which seemed to be just a bunch of timeskips and pictures followed by kisses and "i love you" over and over.Easy way would have been making a full harem, yet they stick to their vision and kept both Val and Zenda romances as solo paths. Knowing how annoying harem fans can be, it does put a smile on my face when devs don't succumb to their demands.
But don't worry, from what I heard it seems Heaven's Door will allow full harem, with new versions of Nicole and Maddie being two of the main love interests... and I believe one of the devs mentioned that Nicole would be some kind of "matriarch" among the harem.
Don't know about the mod and the impregnation error since I haven't played this AVN for about 2 years.