A healthy adult should be fine for 4 days on their own. I'd give him a good meal before you go and leave a fresh salad with him. Make sure the lights are set on timers and optionally set up a webcam so you can check in on him if you want to.
Unfortunately not. His lights and basking bulb are set by a timer.
He will not eat for 4 days. And pooping in his viv is something he moves and stays away from.