Thank you for your post, and I apologize for the late reply.
All blank values in a value list based on a field will not be displayed, even if the second field is showing, since the first field is the one being stored.
A value list sort can only be ascending or descending. A custom sort is not available at this time.
I recommend that you post both of these suggestions to the "Suggest an Idea" board at:
In FileMaker Go, the inability to select the last item in a long value list has been addressed in FileMaker Go 14.0.4.