i doubt the devs still respond to questions on this game (as it is 4+ years old), but i truly cannot get ending 4. i've tried every tip but nothing works. i always end up with 1/2.
I'm not a dev, but I can definitely help you. Ending four was the first ending I got, so it should be pretty simple! All you have to do is gain Brandon's trust and try to convince him you are who you say you are. You also have to treat him with a lot of kindness and tell him how you relate to him whenever given the opportunity.