When you make out with Mahgda,she states why she is certain on why she is pregnant of MC child,she make clear that Dolf dont fuck with her in a long time,and she makes even more clear that he cant know its MC child because he doesnt know its needed to fuck to get her pregnant,so he would never guess that he isnt the father,as for Erevi,she states that when she found necessary,she actually happened to use Bolom to pass time,but its a practice she wasnt making in long time since her"obssession"with huge things passed as her adult age came around and her obssession with mess with even more powerful magic settled in(she would still probably fuck around with him when she felt the need),as for his form,the Imp cant abandon her form,she can improve it,but once it was settled in as the pocket pussy,that is what she will look like,so i think the same rules apply to Bolom,so even if the MC turned to be the last hit on Erevi thoughts,he still couldnt change his form to the MC since he was summoned as something that looked like an Ogre