Do what thou wilt shall be the whole of the Law.
I don't think the original idea of that column was to be complete. It was, rather, to associate certain known formulae with a part of the Tree of Life. I don't know that every part of the Tree needs a separate "formula" in this sense - but there's no reason not to expand the list (individually or collectively) as new specific formulae come to light and are understood.
On the one hand, I think you're confusing Formulae with something like God Names. On the other hand, God Names provide one of the best sets of Formulae. (The Formulae column could then best be understood as "Miscellaneous Additional Formulae Not Already Catalogued In Another Column.")
On possible confusion: I would totally agree with the usability of Had as a Divine Name for Kether within the framework of the Thelemic pantheon. But to fit as a formula in the sense meant by the column, it wouldn't be the Name so much as the series of letters in the Name - immediately raising the question of which spelling you are using? - and the meaning of the sequence of letters themselves in relationship to the Sephirah.
On using Divine Names as Formulae: A.D.N.I. (Adonai) is one of the most important formulae of Malkuth. A.L.H.Y.M. (Elohim) is one of the most important formulae of Binah (perhaps the most important other than the name of the Sephirah itself). And so forth. These are both Names in the theurgic sense, and Formulae in the sense that the sequences of letters themselves have deep and expository meaning; and those two functions overlap.
My thoughts on this Equinox morning...