I don't think his conclusion is good. There's no sitting on the fence here. ὁ θεός is a quasi proper name when not decontextualized away to a false god or a strictly human agent of God per John 10:34-36.His conclusion is good, clearly he could be more decisive, but you read between the lines.
ἐγώ εἰμί ὁ θεός occurs 9 times in the OT and once in the NT (Matt 22:32).
If someone says ἐγώ εἰμί ὁ θεός, and demands it be treated exclusively, then I see that as at least a quasi proper name and so outside of Sharp's rule. It's not just a title, e.g. to be dished out also on those he "begets."