Don't let the "reflections of leaves" crowd fool you. That's how they lull you into inaction while the demons lure you in. You've lived with that in your house for at least ten years? Wow. I'm surprised you are still able to leave the house. Whatever it is in the window does not seem to be trying to escape. This is a "lure you in and trap you for all eternity" scenario. Just wondering: have any realtors refused the commission when you tried to put the house on the market? That's often a tipoff.
Anyhow, you should sell this story to Hollywood asap. A24 would probably pay you big bucks for it. A24 got a critically acclaimed movie out of a sheet with holes in it, so I can only imagine the potential here.