Can you give me a time index? That's a long lesson. I haven't watched most of these since they were first recorded, years ago. I'll have to rewatch that section to get familiar with the material I was covering.

You could add a ToDelete field (Yes/No) to the Table and only delete the records where the value is set to True.
I also added an 'Are you sure' as I do with any DELETE operation.
I called the Renumber Sub so the records are renumbered in one step.

    If MsgBox("Are you sure you want to DELETE the selected contacts?", _
        vbYesNoCancel + vbCritical, "Confirm Delete") = vbYes Then
        CurrentDb.Execute "DELETE FROM ContactT WHERE ToDelete=TRUE"
        Me.Requery
        Renumber
    End If

This was a very long lesson. Start about time 25 when you are talking about deleting multiple records and go to the end. You were not successful in trying to delete multiple records the way you wanted to.  Over the time from 20 something to the end you showed many trials and error tests but did not completely get what you wanted.  Therefor my suggestions.

Ah yes. I like Kevin's solution.

Just realised, the records don't get deleted the first time you hit the button. You have to click a second time.
You need a Me.Refresh before the code I posted above.