Oh don't worry, what I meant is that the internal resolution is different from the game window size. So right now it's always being rendered at 1920x1080, no matter if you make the game size very small or expand it to fit a 4k monitor.
What I have yet to do, is make different resolutions available so people playing with different displays don't have to load the game at 1080p if they have a smaller monitor, or so it doesn't get blurry when playing at huge ones. You'll still be able to change the window size.
But yeah the fullscreen is going to be already in the game in a couple of days when the public gets released so no problem about that! And soon enough I'll make it so you can also choose borderless window, it's easy in the engine I just have to make it an actual option.
The other things you mention I'll also work on! It's just that this kind of thing takes time and I'm just a guy, so I hope you can understand. I'm slowly adding more features and QoL changes all the time, so feedback like yours help me taking note of problems. They will be addressed.
Also the blue markers are meant to show parts where you don't see a door. If you see a door, there's no reason for a marker, but if there was no marker when at the end of a corridor I feel it would be confusing. About interactions, that's a bit more random yeah XD