Παῦλος ἀπόστολος, οὐκ ἀπ’ ἀνθρώπων οὐδὲ δι’ ἀνθρώπου ἀλλὰ διὰ Ἰησοῦ Χριστοῦ καὶ Θεοῦ Πατρὸς τοῦ ἐγείραντος αὐτὸν ἐκ νεκρῶν,
Notice the two sets of nouns in simple apposition, the first set in black and the second in red. Παῦλος, the first noun of the first set is unquestionably a proper name, and the second noun of the first set ,ἀπόστολος, is a title which is the functional equivalent of a proper name because it can only refer to Παῦλος. The apostle's M.O. with such appositional phrases seems to be to put the proper name first. Thus looking at the second appositional phrase ( Θεοῦ Πατρὸς) it is obvious that Θεός is seen by the apostle as a proper name of the Father also. Regardless, if it is not admitted that it is a proper name, it must be seen at least as the functional equivalent of it.