Get your featured tab set as default and have your featured video on autoplay first and foremost, you want every view from people visiting your channel
Heres two guides:
http://yttalk.com/threads/turn-off-always-take-subscribed-users-to-the-feed-tab.913/
http://yttalk.com/threads/turning-on-autoplay-for-your-featured-video-on-youtube.745/
I think if you shorten the intro you could try adding some pub noises like you do throughout the video, maybe having some voice say "It's Friday night, time for the Tube Inn" or something fun I dont know but something a lot shorter and more fitting, the music is very serious sounding and energetic, type of thing you will see when someone is running from the police or something.
I think in your videos it would be good if you seemed a bit happier for example you could say "Alright everyone, welcome to the Tube Inn, take a seat, grab your pint and get your thinking caps on" or something like that, something a bit fun or something you would expect a bingo caller to say at the start of the night if you get what I mean. Throwing in a few jokes in here and there where they would be appropriate. That could even work as an introduction.
You could do with some sound effects you could use in every video, for example when you mention the promotion a sound effect like this one here could be good:
http://soungle.com/index.php (search for whistle and I think its the Sexy Whistle one)
I am thinking a long the lines of the types of noises you would hear in a pub if someone could win a big bottle of champagne and everyones already a bit drunk, men shouting "Wahey" etc and women doing the whistle lol if you could mix those two that would be great.
When you say you are disappointed a sound effect could be appropriate as well like one of them failing sound effects or like the fail buzzer on Countdown I think it was, or you could even use a sighing audience effect there.
Other than the green screen/lighting issues I cant think of much more right now. Good luck with your channel Quiz