Uhm, so... Creaking got MUCH worse in a day and witohout any reason at all, so I decided to mess with the screws again.
While I was loosening one of them, screen made audible creak without any pressure applied by me or anything.
So, now I'm sitting here, trying to twist the phone (with screws noticeably loose) in my hand, and, well, nothing happens. No creaks, no clicks. What the...
Looks like my initial conclusion was totally wrong: screws DO apply enough tension to hold the phone together. Not only that but they basically apply too much tension.
Good idea, I will remove the 2 screws so that my phone wont click anymore. Goodbye "clickgate"