Wait! So is Ferris Carol's mom? i'm too lazy to read the whole hing again

Yes.

Do you know if that guy who proposed is the biological dad?

I think thats why he was all "what have I done," and nothings been shown that says he isn't the father. Based on Carol's life style and her mom's personality I think he is the dad.

All I could think when reading this chapter was does this count as statutory rape?

he probably is, his last name is Olston like Carols