If you want ti get ending 1 you need to struggle while Grim connects you two.
Can you also share how did you get ending 2 and 5?
And I don't know anything about 4.
thank you for your response! Update: I got ending 1, I hated it. But thank you for your clue, it definitely helped :)
For ending 2 you have to be selfless; when Grim tells you about your soul, you have to reply with "I don't mind. I'll take the sickness. The taint" + the next answer also has to be darker, and more selfless. You will know you got this ending when the room is dark instead of bright.
For ending 5 you have to keep choosing the marriage option every time you are prompted, I'm pretty sure the final marriage answer "How about a shotgun wedding?" triggers it.