Do you have a camera? Can you see your kid and make sure nobody gets in? If so, yes. That’s like living in a 2 story house and going to the kitchen to cook something while the kid sleeps. He’s 4.5, he know how to get off bed and even go outside to look for you if he needed you
Yes.
You'll be okay mom. I live in a house, 13 steps to get to 2nd floor, I'll work on the main or basement but have camera on him in case of anything. Also depends, does your little sleep the entire night?