1. you get Lexy's by not help the animatronics you will see her at the bar and you can talk her and she will tell you to go to the shop that sell the protection ward
2.im not sure i think you get the true ending if you do as you said but also free everyone from afton on night 13 not 14 but im not sure
3.you can get six ending the stars show when you get an ending
4.what color are your three stars? btw sorry if my answers were not clear enough