If the universe is expanding at the speed of light...
The universe is not expanding at the speed of light. If it was, you wouldn't be able to see the computer screen in front of your face! (The light from the computer screen couldn't reach your eyes because the space between you and the screen would be expanding faster than the speed of light).
The universe is actually expanding really slowly. It's just that if you have a lot of space expanding slowly, it adds up to a very fast, overall expansion. This can become greater than the speed of light. This is where the stuff you're talking about can happen.
Yes. m=e/(c2) Just re-arrange the equation as you would with any basic algebra equation. There's nothing that special about this equation
Does the fact that the loss of a little mass producing a vast amount of energy work the other way round?
I would guess that the logistics might get a bit complicated and more involved. But in a word, I would guess "yes."
...then it is obvious somthing amazing has happened to produce such quantities of mass?
Yes. The Big Bang is pretty amazing, if you start being able to understand what's going on. Unfortunately, I'm not there yet. But I like to pretend I am sometimes.
As you can tell i have a million questions any help in answering them would be great.
No one's here to do your homework But lots of people enjoy answering questions. Ask away, the worst that's going to happen is it won't get answered. The best that's going to happen is that you'll learn something you didn't know before. I'd say the reward outweighs the risk.