I am sorry you are having these problems. Some guests will ask and ask and you need to be polite and professional - but firm. You are running a business.
Experienced hosts will tell you there are red flags. One was asking for an early check in. I would have refused or charged him an extra day.
I wasn't clear what you mean when you say he didn't specify how many people were turning up. He must have booked for a fixed number of people ie 1, 2, 3, 4 etc Which was it?
Do you charge for additional people to stay at your property? If so and you are happy for them to stay, you need to go into your booking and amend the booking say from 1 to 4 people (you don't charge for infants). While you are at it, also amend the booking for the extra night.
Of course if you asked the guest if he should pay he is going to say no. It isn't up to him. It's up to you. It's your property !!!!
Let your guest know what he will need to accept the amendment for the extra people and extra night if he would like to stay at your place.
If he doesn't by say tomorrow morning, I would ask Airbnb to cancel the booking as the guest makes you feel uncomfortable.