C1 unit 1 modal verbs - right or wrong?

He could tell us he was going to be late! Now the party is half over.

I wonder why John didn't come to the party last night. He might have to work late.

Drive slowly on that road. You may well see a bear there.

That guy can't have been George Clooney. He wasn't with Amal.

He maybe said some bad things to her, but he's actually a nice guy.

It's an awful rainy day. We can as well go to the cinema.