Tefillin and Teaching One's Children: An Observation

I realized this over Shabbat. All 4 places where the Mitzvah of tefillin is addressed in the Torah also talk about something that must be transmitted to future generations.
Moreover, in Bo it's unclear textually whether the references to tefillin are part of the formula that the father is supposed to use to answer his son, or part of what God is exhorting the father to do in order to make sure that the relevant messages are perpeutuated.
The two more well-known references both contain exhortations to teach your children. In fact, a case can be made, more easily for 'Ve-haya im shamo'a', that the mitzva of tefillin is a vehicle for effectively teaching one's child.

I'm not really sure what to make of this. Are tefillin designed to be some sort of concrete object of memory - like the pesach, matzah, and maror that also appear in this context?
Could it be that, from a literary perspective, it's not referring to tefillin at all - rather it's saying that in addition to instruction, the father must provide visual and tactile elements into his child-raising? It's easier to read that into 'zikaron', harder for 'totafot'.

And if this is how the Torah frames tefillin, how and when did the symbolism of tefillin become one of a romance between God and the Jewish people (i.e., the notion of 've-eirastich', the Aggadot about what it says in God's tefillin, the themes of the 'le-shem yichud')?

something to think about during chazarat ha-shatz.
SHR