After several attempts, I can confirm night 6 is possible (if anyone was curious). It's definitely a lot harder than original 4/20 mode, but still quite fun.
Also, not sure if it's a bug or not, but there were several times where Foxy would leave his cove, but as long as I didn't look at the left hall camera, he wouldn't jumpscare me (sometimes he would, sometimes he wouldn't, not sure why)
Overall, a very enjoyable game