Very nice. I was a little concernend that your volunteer on the second video was going to be to boisterous and distracting to the audience but his reaction at the end was even better as he went from being a loud-mouthed show-off to a quiet little confused church mouse.
Also, going by the first vid, it would appear to be a very bad idea to tell a drunken university audience to talk amongst themselves for a bit. Maybe you could have some horrible lift music playing whilst you do your bit with your volunteer in future. The tackier the better as it could get some laughs out of the audience which would be attributed to you rather than themselves- if they can amuse themselves by joking around, they don't really need you which is why you had a struggle getting their attention back afterwards.
On the whole, it was very good, and if you can hold your own whilst facing that audience, you shouldn't have any worries with more sedate crowds.