It's hard to tell. Cats are perfectly happy outside for long periods if they have access to food. But it's not clear from your posts whether this cat is not being provided with food or not, unless I have missed something. Didn't you say it has a catflap now?
I don’t think there is anybody upstairs today... I am pretty sure I heard some human footsteps this morning but that was it.
Is it about time I start feeling sorry for stalker cat?