There is nothing significant that I can add here. Helios is certainly correct that the reading at PE 17, p. 35 should be _Dornhabar_. And what is visible of the letter in ball-point obscured by the "D" is shaped like an "N" so the occurrence of _Nornhabar_ = _Dwarrowdelf_ in _War of the Jewels_ makes it beyond doubt that an original _Nornhabar_ was emended to _Dornhabar_; and this is the reason for Tolkien rewriting the form, as Carl observes.
It is interesting to note the possibility that the second element of this name, also seen in _Anghabar_ 'Iron-delvings' (Silm. 138, 316), is related to Q _sap-_ 'dig' in the "Qenya Word-lists" (PE 16, 145). Is this an unusual case of a root persisting in Tolkien's conception without being listed in "The Etymologies"?
-- Christopher Gilson