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"However, there comes a point of internalization, when one realizes, aha!, God has specific intentions concerning my life and I have an individual call to respond from the heart."

We call this "metanoia", when we become totally changed such that our focus shifts from ourselves to God. This may be the conscious beginning of the process of theosis. As you may know, Orthodoxy does not accept Blessed Augustine's concept of Original Sin nor its Protestant expression of the utter depravity of the unbaptized soul. Thus, Orthodoxy holds that there subsists in the soul of every fallen human ever so much of a "spark" of our pre Fall state that yearns for God. It is that "spark" which responds, cooperates, very individually, to the first call of God's grace in baptism.

"Catholics and Orthodox disagree about the way in which the Father, the Son, the Liturgy, etc. interact, as well"

We have thought for about 1000 years that we disagree on the "internal dynamics" of the Trinity and indeed we might, but its beginning to appear that the filioque controversy may have its origins in a failure of Latin to speak clearly about a concept which was defined in Greek. I am unaware of any differences between Rome and the East on what is going on in the Liturgy, but I will say that transubstantiation seems to be a particularly inadequate, because it is human thought, way to describe or explain the great Mystery of the Real Presence of Christ in the Eucharist.

Tell me, do you believe that the average person, you, me, the rest of us here on FR and not spiritual super athletes like holy hermits, can be saved, or attain theosis, outside the boundaries of the visible Church on earth. When I use the term Church here, I am meaning, for the purposes of this question, any organized collection of Trinitarian Christians?

I don't know quite how to phase a single, general answer but, I sense a dynamic among a few half-answers:
It cannot be sought after in any other body.
God seeks unity in the Church.
An aversion to brotherly communion is ... a bad sign.
We are predestined to "be conformed to the likeness of the Son" and no geographical separation can thwart God's will. (Oops, we just lost any Calvinist lurkers;)