Are the concepts of being from and through the same?
From the Latin pov, only in terms of second causes. In terms of First Cause, there is only one (the Father), and the term “through” does not come into the equation.
I’m not sure how one can draw the conclusion that the Spirit is from the Son from the statement that the Spirit is from the Father through the Son.
Latin theology does not claim - nor has ever claimed - that the Spirit is from the Son in terms of hypostasis. When the Fathers (Latin and Eastern) say that the HS is from the Father through the Son, they refer either to the Mission of the HS, or the Substance/Essence of the HS, not the Person of the HS.
Almost all of the Eastern fathers who speak of the Spirit being from the Father through the Son will state in the same passage that the Spirit is clearly not from the Son (st. John of Damascus for example says that the Spirit is projected from the Father through the Son, but that while it is the Spirit of the Son, it is clearly not the Spirit from the Son).
Yes. Florence does NOT say that the Son is the cause of the
hypostasis of the HS(which is equivalent to saying that the Person of the HS is from the Son); rather it says quite plainly that the Son is the cause (along with the Father) of the
hypartzia of the HS (which is equivalent to saying that the Essence/Substance of the HS is from the Son).
In the Eastern line of thought at least, the formula from the Father through the Son (but not from the Son) seems to be interpreted as meaning that the Spirit proceeds from the Father hypostatically (in this way the Spirit can be neither from nor through the Son), but that the uncreated energies of the trinity are manifest in or shine forth in the Spirit from the Father through the Son.
Yes.
That is the same thing that the Latins teach, EXCEPT that while the Latins (like the Easterns) distinguish between the
hypostasis and the Essence, Latins do not distinguish between the uncreated Energy and the Essence. The difference between the Latin teaching and a certain polemic in modern EO’xy is that (I have noticed) many EO today claim that the manifestation of the Spirit through the Son is a merely temporal activity of the Godhead, whereas the Synod of Blarchanae and St. Palamas both teach that it is an ETERNAL activity of the Godhead. In this, the Latins are closer to the medieval Easterns than modern EO are to their forebears.
The idea of the Son causing the ousia of the Spirit looks very foreign in Byzantine theology
That should present no problem. The Latins
do not teach that the Son is the Source of the
ousia of the Spirit. The Son is cause (along with the Father) of the
ousia of the Spirit, but the Source of the
ousia is the Father alone. Please realize and remember that. Just remember that what the Easterns understand as “cause” is more nuanced in Latin theology.
because the act of generation (either begetting or procession) involves the Father generating a hypostasis with the same divine essence which he possesses (that is hypostatic and essential procession or generation are the same act).
Hypostatic and Essential procession/generation are NOT the same acts, though they both occur at the same moment of eternity. When the Fathers unanimously teach that “
all the Holy Spirit has He receives from the Son,” the Fathers are obviously distinguishing between the hypostatic generation and the attribution of properties (including Divinity, which Easterns would call the Essence). The idea presupposes a subject Who is receiving from the Son. So the hypostatic generation of the Holy Spirit occurs distinctly from the attribution of divinity and other properties from the Son.
The thought, then, that essence can proceed from or be caused by any but the Father looks like total nonsense because the justification for the idea (the consubstantiality of the trinity) would then have the inverse implication that either the Son is begotten essentially of the Father and the Holy Spirit (because they are coeternal and consubstantial)
Do you notice the mistake in your syllogism? Your rhetoric depends on the phrase “
be caused by ANY but the Father.” But the Latins don’t claim that ANY can be “second cause.” The Latins teach that ONLY the SON is “second cause” in the Trinity. The property of being “second cause” (or, in more Eastern terms, the property of being “through”) is a hypostatic property of the Son. So the implications you propose are invalid non-sequiturs because it depends on an invalid premise.
or worse yet indicate that there was a time when the Father and Son were but the Spirit was not (that the Spirit is not coeternal).
That’s the same argument that Arians and Pneumatomachi used against the orthodox Fathers, so I don’t think we need to entertain such thoughts.
That at least is my major obstacle to ever being able to understand the filioque as an Orthodox teaching. I’m not sure how the filioque can not violate the monarchy of the Father, especially when the procession through the son is said to happen in essence.
It’s easy once you accept that the Latins distinguish between “Source” and “cause.” Just because the Latins consider the Son a “cause” does not mean that they regard Him as “source.”
Edit: I fear we are digressing from the topic of this thread, perhaps it would be best to take this filioque tangent elsewhere.
Agreed.

If the Mod is reading this, perhaps she can split off the appropriate posts to another thread entitled “Filioque - Distinguishing the Essence and Person of the Holy Spirit.”
Blessings,
Marduk