How, too, did he come to have the paraphrastic reading of Matt.v.16 which is found in no MSS.

or versions but in Justin (approximately), Clement of Alexandria, and several Latin Fathers?
The paraphrase might naturally enough occur to a single writer here or there, but the extent of the coincidence is remarkable.
Perhaps we are to see here another sign of the study bestowed by the Fathers upon the writings of their predecessors leading to an unconscious or semi-conscious reproduction of their deviations.

It is a noticeable fact that in regard to the order of the clauses in Matt.v.4, 5, Tertullian has preserved what is probably the right reading along with b alone, the other copies of the Old Latin (all except the revised f) with the Curetonian Syriac having gone wrong.

On the whole the complexities and cross relations are less, and the genealogical tree holds good to a greater extent, than we might have been prepared for.

The hypothesis that Tertullian used a manuscript in the main resembling b of the Old Latin satisfies most elements of the problem.
But the merest glance at these phenomena must be enough to show that the Tuebingen theory, or any theory which attributes a late origin to our Gospels, is out of the question.