A comma naturally exists here, both in Greek and in English, but there is no reason why τὸ κατὰ σάρκα ends the sentence, which is what you have been arguing and have not adequately supported. A sentence can be composed of more than one "clause."
But if the clause is the last clause in a sentence, then it will end the sentence.
The rest of your argument here is a dodge, and effectively you refute yourself:
We have a prepositional phrase: κατὰ σάρκα. When the neuter article substantivizes the accusative case with a prepositional phrase, it signals the function is adverbial. Thus, in Romans 9:5, τὸ κατὰ σάρκα it modifies the action implicit in ἐξ ὧν. This is not "far too complex an argument," it's actually a statement of how the grammatical structure works.
That wasn't the point I was getting at.
The point is that the whole clause from ἐξ ὧν onward is affected.
It is your argument that is far too subtle and relies on an ambiguous usage of the English comma, even a synthesis of English comma usage and Greek grammar.
By inserting an English comma, you can appear to continue the ἐξ ὧν clause in English. But as to the Greek grammar, your thesis is a contradiction in terms.
For if τὸ κατὰ σάρκα modifies the action implicit in ἐξ ὧν, then the action is modified irrevocably. You want to carry on the ἐξ ὧν clause, as if the action implicit in ἐξ ὧν hadn't been modified: as if you were talking about Christ according to the Spirit. That's impossibe, because ὁ Χριστὸς is bound by the modifier.
So you have to put a full stop, not a comma, after τὸ κατὰ σάρκα, because it ends the last clause in the sentence.
In English we would add commas before and after, but there is a continuation of the same thought that is unhindered by τὸ κατὰ σάρκα in Acts 2:30: ἐκ καρποῦ τῆς ὀσφύος αὐτοῦ τὸ κατὰ σάρκα ἀναστήσειν τὸν Χριστὸν: "that of the fruit of his loins [τὸ κατὰ σάρκα] he would raise up Christ to sit on his throne." How is it that it doesn't end the sentence in 2:30, when it falls in the middle of a thought, but it can't be so in Romans 9:5? There is nothing artificial about any of this.
Do you and TRJM have anything better to do than make up rules on the fly? First learn the language. Then use it rightly.
What applies in Acts 2:30 doesn't apply in Rom 9:5.
As I said before the τὸ κατὰ σάρκα clause in Acts 2:30 is parenthetical. And if you look at an interlinear, you will see it clearly (e.g. ABP at biblehub). It can be removed and the sentence remains intact, before and after the τὸ κατὰ σάρκα clause.
But Rom 9:5 is completely different. If you remove καὶ ἐξ ὧν ὁ Χριστὸς τὸ κατὰ σάρκα, then you must end the sentence after ὧν οἱ πατέρες, There is no parenthesis. Therefore the sentence doesn't continue.