How can I handle this in the least harmful way to him?
You ended things with your fiancé through a text message… That is up there for worst ways to do it.
The damage is done. He was going to be hurt regardless of method.
You say you want to make him feel better. But from the sounds of this, you won't be doing this for him, you're doing this for yourself, attempting to satisfy your own guilt.
press charges. who cares if it’s your sister she literally abused you and could’ve killed you
How can I handle this in the least harmful way to him?
You ended things with your fiancé through a text message… That is up there for worst ways to do it.
The damage is done. He was going to be hurt regardless of method.
You say you want to make him feel better. But from the sounds of this, you won't be doing this for him, you're doing this for yourself, attempting to satisfy your own guilt.
You should be doing nothing.
Let him be.
Break up with this freak