I really cannot figure out the path to the "happy" ending. Does anyone know?
(Vaguely describing each option to select. SPOILERS)
The "Happy Ending" comes from being vague and not letting Cecil learn about the extent of their relationship.
Don't tell him about the marriage. Accept the fact that Cecil is gone and try to give him room to breathe, or try to end things yourself.
Don't tell stories about the past, and do not sugarcoat the way he died.
The way Cecil died was sloppy and painful. You would have given him a swift end. Let him know this.
Make no mention of falling in love.
If given the option to, do not hurt him. But perhaps a better ending comes from moving on