My problem is the power; any advice?

Use your power sparingly and only if it's a necessity to do so. If Freddy makes it to the east hall corner, always close the right door when using the camera. A method I used to beat 4/20 mode is to look at east hall corner, close camera, look at right door light, close if someone's there, open camera, close camera, look at left door light and close door if necessary, repeat. You should have around 1% to 6% power, but if you run out it isn't hard to win because you're extremely close to 6:00 AM. The reason Foxy wont kill you if you use that method is because having the camera up is stopping Foxy from progressing.