We call "uncreated energy" created, so there is a distinction between "Essence" and "energy".
I am not an expert on all this, but I see the Tridentine definition of sanctifying grace as "God's justice, not by means of which HE is Himself just, but by which He makes us just". This excludes the identity of Grace with the Holy Spirit. Romans 5:5 is cited: "The charity of God is poured forth in our heart by the Holy Spirit, who is given to us"
The Holy Spirit is the mediator of the love of God, which is given to us int he justification, and is therefore distinguished from Sanctifying Grace, as the gift from the giver...
Grace is, however, a participation in the Divine Nature. For example, the Church in the Liturgy says "Grant that by the mystery of this water and wine, we may be made partakers of His divinity who vouchsafed to become partaker of our humanity". In the Preface of the Feast of Christ's Ascension into Heaven "He was assumed into Heaven in order that we might be partakers in His divinity".
According to 2 Peter 1:4, we are elevated to participation in the Divine Nature. Other Scriptures cite indirectly that we participate in the Divine Nature by an elevation of our humanity to the Divine - BY GOD - as generation consists in the communication of the nature of the Generator to the generated. I am probably saying nothing new to you here. This is esp. noted by St. Athanasius famous quote "The Word became man, so that we might become God". The point of this is that Catholics believe the same thing, expressed differently. The West considers the sacraments ex opere operato, the sacrament is completed by the completed sacramental rite, because the priest is considered in the person of Christ. What is the action of the priest in the East?
The Treasury of Merits is based more on the Body of Christ and our participation as part of the Communion of Saints then in the Trinity's created vs uncreated energies.
All in all, an Ecumenical Council has not defined this area, so I don't see a right or wrong on this matter.
Regards
" Grace is, however, a participation in the Divine Nature."
This is denied by the Eastern Fathers and Orthodoxy if what you mean by Divine Nature is the Divine Essence. Now if in fact you do mean the Divine Essence, then, as both +Gregory Palamas and Yannaras point out, so called created grace becomes an absolute necessity for your theology to work out.
Jo, this theological difference, perhaps even more so than even the issues surrounding the appropriate exercise of Petrine authority, is where ultimately any attempt at reunion will likely founder.
Because of the Roman belief in created grace, your priests, for example, have to act in the person of Christ at the Eucharist or other sacraments, almost as some sort of magician. By establishing the theory of created grace and either denying or ignoring the distinction between the Divine Essence and the uncreated Divine Energies, the epiklesis in the Divine Liturgy disappears. Its not the Holy Spirit, or uncreated Divine Energies which changes the bread and wine into the Body and Blood, but rather by the words of the priest. The same goes for the rubrics of confession. The priest absolves (absolvo te). If you think about it, Jo, without the distinction between Divine Essence and uncreated Divine Energies, or for that matter, the division of the uncreated energies into created and uncreated grace, much of Western theology begins to fall apart, certainly, the whole concept of the Magisterium and the Treasury of Merits goes out the window and with that indulgences and likely the Augustinian concept of Original Sin (and its necessary corrollary, the Immaculate Conception) and perhaps even purgatory.