The first thing you gotta understand about the dead is that even if they manage to cling to the afterlife and retain a sense of themselves, they only have access to one verb, and that verb is "haunt". Without a medium like me who knows how to channel their voice and give them words, breaking all the glass in the kitchen is the only way to get your attention and making your friends foam at the mouth and chant gibberish is their best attempt at speaking to you. It doesn't mean they meant you or Samantha any harm. It's important that you understand that.
When you said who you thought it was haunting you? You were half right. The couple who sold you this house, the husband said his mom died here? Well, that's not strictly true. Turns out, it was his dad. And he has unfinished business that he wants you to deal with.
The second thing you gotta understand about the dead is that they don't really have the same concept of privacy that the living do. Or, it's more accurate to say that they can't. When that haunt a something, they more or less become that thing. Its spirit. Technically, its primary nooperceptual locus. Doesn't matter. Point is, if they're haunting a house, they "see" whatever happens in it. They don't even really understand anymore why that would be a problem. It's not personal, just a side effect of the consciousness shift.
So, when I tell you that your entity, the dad, saw you, um, become... transgender? Transition. Right. When he saw you transition, it's not like he was a living person looking in your window while you changed. He just knows because the walls and floors know. And apparently he didn't know, before you arrived. That that was a thing. That people could just... do that.
So. What he wants you to do is talk to his son and tell him that his mom was actually his dad, and get him to update the headstone. His name is Martin. Which, you know, it's hard for the dead to convey specific words. It's mostly just emotions and imagery, which is what makes my job so interesting. But this came through really strong. "Martin".
He seems pretty confident that his son will be cool about this, especially if someone who gets it talks him through what it means. And if he doesn't? Well, the third thing you gotta understand about the dead is that if you piss them off, they get mean. So let's hope that this guy is just happy to have gained a father from beyond the grave.