Aqwsed, unfortunately Rom. 9:5 is not as clear cut as you make out. You have given one side of the argument, so I won't go into it. Grammar, Paul's theology and scribal error should all be weighed up for each to come to his own conclusion. The following is Rom. 9:5. Footnote 1 in Metzger's commentary:
Among many earlier discussions pro and con, two may be singled out for special mention as representative of the two points of view. In favor of taking the words as an ascription to Christ, see William Sanday and A. C. Headlam, A Critical and Exegetical Commentary on the Epistle to the Romans, 2nd ed. (New York, 1896), pp. 233–238; in favor of taking the words separately from the preceding clause, see Ezra Abbot, “On the Construction of Romans ix.5,” Journal of the Society of Biblical Literature and Exegesis, 1881, pp. 87–154, and idem, “Recent Discussions of Romans ix.5,” ibid., 1883, pp. 90–112 (both articles are reprinted in Abbot’s posthumously published volume entitled, The Authorship of the Fourth Gospel and Other Critical Essays [Boston, 1888], pp. 332–410, and 411–438). For a more recent discussion, see the present writer’s contribution to Christ and Spirit in the New Testament; Studies in honour of C. F. D. Moule, ed. by Barnabas Lindars and Stephen S. Smalley (Cambridge University Press, 1973), pp. 95–112; reprinted in Metzger’s New Testament Studies (Leiden, 1980), pp. 56–74.
On the other hand, in the opinion of others of the Committee, none of these considerations seemed to be decisive, particularly since nowhere else in his genuine epistles does Paul ever designate ὁ Χριστός as θεός. In fact, on the basis of the general tenor of his theology it was considered tantamount to impossible that Paul would have expressed Christ’s greatness by calling him God blessed for ever.
Bruce Manning Metzger, United Bible Societies, A Textual Commentary on the Greek New Testament, Second Edition a Companion Volume to the United Bible Societies’ Greek New Testament (4th Rev. Ed.) (London; New York: United Bible Societies, 1994), 459–462.
On the other hand, Paul nowhere else in his genuine epistles (that is, the letters which scholars agree were written by Paul; Titus 2:13 is generally regarded as not written by Paul) ever designates ὁ Χριστὸς as θεός. On the basis of the general perspective of Paul’s theology, it is difficult to think that Paul would have expressed Christ’s greatness by calling him God blessed for ever.
It is also possible that a copyist accidentally wrote ὁ ὥν (the one being) for ὧν ὁ (of whom). That is, the original text may have read “4 … of whom the sonship (ὧν ἡ υἱοθεσία), the glory … 5 of whom the patriarchs (ὧν οἱ πατέρες), and from whom (ἐξ ὧν) the Messiah according to the flesh, of whom God over all (ὧν ὁ ἐπὶ πάντων θεός).…” This punctuation “would make Paul assert that Christ by natural descent is a prerogative of Israel, but that God is the one who is preeminent and blest forever, in effect, Israel’s ninth prerogative” (Fitzmyer, p. 549). It should be noted, however, that there is no evidence in the manuscripts to support such a correction of the text.
Roger L. Omanson and Bruce Manning Metzger, A Textual Guide to the Greek New Testament: An Adaptation of Bruce M. Metzger’s Textual Commentary for the Needs of Translators (Stuttgart: Deutsche Bibelgesellschaft, 2006), 308–310.