He just sounds stressed to me. Give him frequent breaks from all craziness around the holidays. I don't think it is necessarily fair to expect him to be perfect when all of that activity is going on. One of my dogs gets a stressed more easily than the others so I limit her exposure to large crowds of people, particularly when she is tired. When dogs get stressed, it can get more difficult for them to respond to commands they more reliably respond to under normal circumstances. Plus they can act out.
I agree about the stress. So, with that in mind, maybe give him a rigorous exercise before the party starts and then, after awhile….the 'break' could be a walk with a number of the guests even around the block to help the trust with the extended number of people in his world! Just a thought!