The bolding of Hebrew fonts appears to have nothing to do with the content controls nor the macro, both of which are working correctly. If you type a simple length of Hebrew text, and bold that, it doesn't change, but the bold flag is set. I regret I don't know enough about the internal workings of fonts to explain this.
One answer is to use a contrasting font. For the purpose of experiment I downloaded the fonts Rubik and Suez One from
http://freefonts.co.il/ and installed them in Windows. I then modified the code to switch the fonts as follows. This does work with your additional example, using a function to provide the formatting.
Code:
Case "DDA"
SetFont ContentControl.Range, "Suez One", True
SetFont ActiveDocument.SelectContentControlsByTag("DDB").Item(1).Range
SetFont ActiveDocument.SelectContentControlsByTag("DDC").Item(1).Range
SetFont ActiveDocument.SelectContentControlsByTag("DDD").Item(1).Range
SetFont ActiveDocument.SelectContentControlsByTag("DDE").Item(1).Range
SetFont ActiveDocument.SelectContentControlsByTag("DDF").Item(1).Range
Case "DDB"
SetFont ContentControl.Range, "Suez One", True
SetFont ActiveDocument.SelectContentControlsByTag("DDA").Item(1).Range
SetFont ActiveDocument.SelectContentControlsByTag("DDC").Item(1).Range
SetFont ActiveDocument.SelectContentControlsByTag("DDD").Item(1).Range
SetFont ActiveDocument.SelectContentControlsByTag("DDE").Item(1).Range
SetFont ActiveDocument.SelectContentControlsByTag("DDF").Item(1).Range
Case "DDC"
SetFont ContentControl.Range, "Suez One", True
SetFont ActiveDocument.SelectContentControlsByTag("DDA").Item(1).Range
SetFont ActiveDocument.SelectContentControlsByTag("DDB").Item(1).Range
SetFont ActiveDocument.SelectContentControlsByTag("DDD").Item(1).Range
SetFont ActiveDocument.SelectContentControlsByTag("DDE").Item(1).Range
SetFont ActiveDocument.SelectContentControlsByTag("DDF").Item(1).Range
Case "DDD"
SetFont ContentControl.Range, "Suez One", True
SetFont ActiveDocument.SelectContentControlsByTag("DDA").Item(1).Range
SetFont ActiveDocument.SelectContentControlsByTag("DDB").Item(1).Range
SetFont ActiveDocument.SelectContentControlsByTag("DDC").Item(1).Range
SetFont ActiveDocument.SelectContentControlsByTag("DDE").Item(1).Range
SetFont ActiveDocument.SelectContentControlsByTag("DDF").Item(1).Range
Case "DDE"
ContentControl.Range.Font.Name = "Suez One"
ContentControl.Range.Font.Bold = True
SetFont ActiveDocument.SelectContentControlsByTag("DDA").Item(1).Range
SetFont ActiveDocument.SelectContentControlsByTag("DDB").Item(1).Range
SetFont ActiveDocument.SelectContentControlsByTag("DDC").Item(1).Range
SetFont ActiveDocument.SelectContentControlsByTag("DDD").Item(1).Range
SetFont ActiveDocument.SelectContentControlsByTag("DDF").Item(1).Range
Case "DDF"
ContentControl.Range.Font.Name = "Suez One"
ContentControl.Range.Font.Bold = True
SetFont ActiveDocument.SelectContentControlsByTag("DDA").Item(1).Range
SetFont ActiveDocument.SelectContentControlsByTag("DDB").Item(1).Range
SetFont ActiveDocument.SelectContentControlsByTag("DDC").Item(1).Range
SetFont ActiveDocument.SelectContentControlsByTag("DDD").Item(1).Range
SetFont ActiveDocument.SelectContentControlsByTag("DDE").Item(1).Range
Case Else
End Select
End Sub
Sub SetFont(oRng As Range, Optional sFont As String = "Rubik", Optional bBold As Boolean)
oRng.Font.Name = sFont
oRng.Font.Bold = bBold
End Sub