The most important question you both need to answer is which is more important: Friendship or the business?
If it's friendship then don't involve lawyers (that will almost certainly end it) and find a way to part under terms such that you can remain friends. In this case don't worry about plus or minus ten percent. It won't matter. Go your separate ways and preserve your mutual peace-of-mind.
If it's friendship then don't involve lawyers (that will almost certainly end it) and find a way to part under terms such that you can remain friends. In this case don't worry about plus or minus ten percent. It won't matter. Go your separate ways and preserve your mutual peace-of-mind.