As regards “name and form” and the Sutta passage quoted above (18 elements), in the Suttas “consciousness” is never included under “name” (nama).
That’s not correct. In some Sutta contexts nāma includes consciousness, in others it merely entails it. An example of the former can be seen in the Attadaṇḍa Sutta and Sāriputta’s niddesa to it. The verse in question reads:
sabbaso nāmarūpasmiṃ, yassa natthi mamāyitaṃ,
asatā ca na socati, sa ve loke na jīyati.
For whom there is no owning of name and matter,
Who sorrows not over what does not exist,
He truly incurs no loss in this world.
In his niddesa to this verse, Sāriputta defines nāmarūpa thus:
nāman ti cattāro arūpino khandhā. rūpan ti cattāro ca mahābhūtā, catunnañca mahābhūtānaṃ upādāya rūpaṃ.
“Name” is the four immaterial aggregates [i.e. vedanā, saññā, sankhārā, viññāṇa]; “matter” is the four great elements and matter derived from the four great elements.”
(Nidd. ii. 435)
The early texts don’t support a body/mind dualism, which is implied by the translation of nama-rupa as “mentality and materiality”
I don’t think the translation implies a body/mind dualism, any more than does, say, that sutta where the Buddha states that it would be less foolish to take the body as self than to take the mind as self, or the Chabbisodhana Sutta (MN. 112) with its six-element analysis (4 great primaries + space + consciousness).