Got some good stuff here. I'll just say that I do wish that there was a "finish" for the monsters after they have their way with the main character enough times. It's not really "mating" without it. Maybe also they could use their abilities while having their fun too, like some electrostimulation for the jellyfish.
Eventually, I would hope that elemental status effects could be added to the elemental spells that you learn. Like the fire spell could cause burning, lightning could paralyze, etc. It'd add some flavor to the battle system past the rock, paper, scissors style it has now.