the police did not ask for your contact address as they have the car rego and the fine goes to whom it is registered to, as you noticed. If the name is misspelled by mistake, this is a human error and not valid for the fine to go away.
In terms what you have agreement with your friend, that goes back to you both to agree on what happens, but why should he pay half if you sped and broke the law, he asked you to drive him, and he gave you his car to use, so i think this is a good deal, if you just drive him only and not use it for your personal use, that is what you need to consider.
The fine will not go away, it will stay and needs to be dealt with,
you can ask for a review, if you have a clean record, then you can ask for caution and you may get it,