IMO your thought that responding the question, "Are you alright?" WOULD be opening up to him. He doesn't need to know. I don't know if it would make him mad but continuing to talk to him will definitely have the greater likelihood of sparking an emotional response...

IMO it was OK to say Happy Holidays. When we walked yesterday--everyone was doing this--it was a holiday with all the good cheer involved....

Hopefully, you are just over worrying about this. Maybe he was just bored and alone....