It would be a lot easier, if you would provide more details on what exactly happens and what you want to happen instead. Looking at your code, it appears, that it is only the first @If statement you have problems with, right?
First off, what kind of field is Approver? Is it a text field or a field of type Names? Does it really just store the common name component of the approvers? That doesn't sound like a good idea to me. What do we have unique canonical names for, if you abbreviate them, potentially taking away uniqueness?
If this is a names field, check from the view level using the properties box what's in the field. @UserName returns a canonical Notes name, and that is just what you want to compare the the contents of a names field.
Finally, if you want to stop the execution of a formula, use @Return().