Thanks for playing the game and leaving a comment! A hint for getting ending 4 is that it's quite similar to getting ending 3, but you have to act friendlier/kinder towards Brandon -- like joking around with him and generally being supportive/encouraging.
Thank you for the helpful reply - I finally got ending 4! At first I thought I'd ended up with the 3rd again, but the subtle differences and the little twist at the end warmed my heart! Thank you again for such a raw, honest game. You guys are a talent!