Alrighty then...
1) Trying to balance a class with different levels can be hard. The best thing is to control, a bit, when and who is speaking. If you are doing oral exercises, you can call upon the lower children and then ask the higher children to repeat or explain what the younger children have said. Also if someone doesn't understand something, get the higher levels to explain. They will probably enjoy the opportunity to help you and also to use their English more.
2) WOW that sounds like WAY too much work. Cut that out! haha Here is what I would suggest. A) I would find some good sources for listening. Get him to watch tv shows, dvds and find some podcasts in business English. Then what you could do it assign a podcast for homework. He listens to it and then needs to summarize it for the next class, making note of expressions that he didn't catch or understand.
Then you can go over a couple things together.
You transcribing meetings is just asking a little bit too much of you.
B) If the student really wants to improve he needs to really surround himself in the accents that are difficult for him. So like I mentioned before, movies, DVDs, music and podcasts in British or Aussie English.
Remind them that it is them that needs to make an effort to improve.
From what you say, it sounds like you are making more of an effort then they are.
Another idea would be...actually a GREAT idea would be for the STUDENT to transcribe the recordings. Get them to transcribe 10 minutes of it. That way THEY are making an effort to understand and repeating it over and over again and researching things.
Then come to class and you can correct and review and fill in the blanks.
I hope that helps.
All the best,
Diana