Existing table data not showing in form through report link

If you have an embedded report on a form and click into Form properties for that report link field, there is a setting there called Editable?  That makes the embedded report editable (ie Grid Editable) when the parent record is in edit mode.

As for the report link field, that will only populate when the form is first loaded, it will not populate if the field on which on which that Report link depends, is edited.  ie the field on the left side of the report link configuration.