I don't think Jas would respond to a vanilla relationship, considering how old she is and the amount of "regular" guys she would have seen and dismissed through her life. I mean look at her job and how she acted towards MC, she clearly was used to being dominant and masculine in interacting with men.
It took MC actually beating her and taking control to get her full respect as well as get her to think that she is a woman, further MC could have easily just went over to smash and move on but chose to rather get her dressed up and take her on an actual date before taking her back home to his place all of which Jas was unsure of. As to the creampie I can agree that was pushing things but as pointed out MB might not want to drag Jas out too much as how many times have we seen her before things actually happened. However even after them having sex Jas was still if MC wanted her or was using her and it took MC to order her to sleep next to him.
I'm not gonna say there are no issues with how it was done but I wouldn't say it pushed MC out of his lovable ass hole character.
The hearing Liz is a good question, but seeing them naked is not an issue as even Nana has slept naked and seen them sleep naked with MC before in the snuggle sessions.