How do I get it to not omit duplicates?
Don't set up your value list like that. Value lists with the use values from a field option, automatically filter out duplicate values from the visible or sorted field.
But what you describe would only enter a last name into the field. The first name does nothing anyway here.
Usually, you'd want a unique ID number for field 1 and a field that combines first and last names--best option is usually a text fields with an auto-entered calculation as field 2.