same! did you ever figure it out? the guide only helps get to that part, not beat it
edit: i figured it out!! bugbear's sucessful ending needs everything mentioned in the guide, but you also need 10 strength before meeting 3 so that you can ask about his smile. you also need to get the prompt in the garden where bugbear tackles you and choose "let him lay on you"
idk if this is needed but i also chose to fight back at the end as well as calling him disgusting but i dont know if those mattered since i tried both without meeting the above condition and it didn't change anything