I refused to agree that my boys were afraid of the dark. "Mommy, I'm scared of the dark! I need the door open!"
No, you aren't. Close your eyes and go to sleep.
My refusal to play along meant that the "afraid of the dark" stage lasted two nights. They never mentioned it again.
Lights out, door closed, no night lights, string lights, flashlights, nothing. We had and still have a nightlight in the hallway and the bathroom so we could see to use the toilet, that's it.
I believe that giving in to the "I'm afraid of the dark, leave all the lights on!" protests only validates that his fears are real. Same with "monster spray." Let's not validate irrational fears. The dark is lovely. At the very most, I'd put a night light in to avoid stubbed toes on the way to the bathroom. I suggest the blue or green LED type. I wouldn't put up string lights or leave on a lamp or hallway light. That's too much. Good luck.