Sorting (album) artist in iTunes
The Artist and Album Artist fields display whatever is recorded in the metadata. In this case, both of these fields contain eason and the duo band.

The only way to change what is displayed is to actually change what is recorded. Your screenshot shows that you already know how to access the metadata (i.e. using the Get Info/Song Info option or pressing commandI) to bring up the details. 

You would need to do that and actually change the information stored there. To do this, make sure you're on the Details tab and edit the info in Artist and/or Album Artist. Once you've clicked OK to save the data, you'll find what is displayed for these songs/albums will also change.

As for the Sort As field, this dictates which field iTunes will use to sort the information, not what is actually displayed in the fields.