Righty, well... I tried to put together a general walkthrough. I think I failed. I feel like I made this game seem WAY more complicated than it is. IN GENERAL, if you do every event leading up to the event at the end of day 5, you have every ending still available to you (except ending 1, which is easily seen by simply doing nothing other than going to sleep).
Hopefully this gibberish makes sense to SOMEONE out there...