How repeating field values ​​in "EntityReference select list widget" as I would with "autocomplete widget"
I found everything I was looking for in the Multiple Selects module. Here is a quote about it (from the module's project page):

... provides a widget called Multiple Selects list for the the following fields types:

entity_reference
node_reference
user_reference
taxonomy_term_reference
list_integer
list_float
list_text
list_boolean
commerce_product_reference

Rather than having a multi-select field, this modules allows you to have multiple select fields with the traditional FieldAPI 'Add another item' button.