You are right to say that sanctification is a present reality, current process, and a future realization. Sanctification is definitely more than a theological category or a stage in the application of salvation to an individual (like conversion, justification, sanctification, etc.). Sanctification is really a descriptive word for *how* God saves. If we consider the fall of man into sin, man underwent a change to his nature that corrupted the good creation of God and resulted in man's perpetual bondage. For man's salvation in Orthodoxy sinful man needs to be transformed back, so to speak. He needs to change, both in his nature (what make someone a human) and in his person (what makes you "you"). Adam's personal sin had a negative-sanctification effect on his human nature, which rendered it and him corrupted and enslaved to sin, death, and the devil. The salvation of Christ through the cross and resurrection applies a positive-sanctification effect that heals and restores man in Christ (to say the least). So in some respects that sanctification - in terms of how Christ sanctified human nature through His Incarnation, and put our sin to death in His flesh through His own death, and triumphed over death with Life in the resurrection - happens objectively outside of us, literally in Christ, and is a pure gift that we cannot cooperate with. In this sense we see Christ as the Second Adam in whom the first Adam finds salvation.
But in the sense that this sanctification of human nature has been applied to the individual person, that's where our energy must unite with God's energy in us, because then the issue is always actualizing what we have in Christ as we make free choices. God gives us what Christ has done in total through Baptism, Chrismation, and the Eucharist, but it depends on our faith as to whether and how we will continue from this. We have the communion of Christ's healed and sanctified human nature, so as Christians we have a saved (sanctified) human nature in common, but my person is not the same as Christ's person is not the same as your person, etc. That which makes me "me" must work out my salvation with fear and trembling, knowing that God is at work in me to actualize the sanctification that Christ has accomplished outside of me and has implanted into me through my communion with Him in the Church.
So sanctification is a word that describes the work of God to save mankind. It is carried out objectively by the work of Christ in the Incarnation, His life, passion, death and resurrection. It is given to me through faith and Baptism-Christmation-Eucharist (these go together). It is actualized throughout that which is uniquely "me" (i.e. my person) through my cooperation with God at work in me (e.g. faith working through love). This is sanctification in Orthodoxy. And this is "salvation."
Some additional thoughts...
In this light we can understand justification. "Sanctification" means literally "to make holy." Justification means literally "to make righteous." In patristic writings, translations of the Scriptures into other languages, and the general liturgical and sacramental context of historic Eastern and Western Christianity the only difference between those two actions is the word "holy" versus "righteous." The essential "how this happens" is the same. In English we tend to call this "how" itself sanctification, which can be a bit confusing.
In time tangential concepts arose in the West about merit, God, the law, and the cross which further obscured the simple teaching retained by the East. Certainly the retention of the Greek language (minimizing the "lost in translation" syndrome) helped to keep the matter focused, while in the West the loss of the nuances of Greek theological language to the less precise, more juridical Latin language helped deprive many devout men of necessary key insights. St. Augustine takes a lot of blame for this, as an early and huge player in Latin theology who himself did not know Greek; but the blame is perhaps better laid at the lack of Greek and not St. Augustine's person.
Yet still for this reason (and others) Western Christians often have a hard time understanding Orthodox thinking on these matters, because in the West the conversation is built on so many alien concepts that arose and ripened in the Western theological climate alone. In order to understand the practice of the Orthodox Church (for that is how we use our theology here) one has to strip down to what seems to be basic concepts and make adjustments to the placement of certain familiar concepts (God's love, judgment, juridicism, sanctification, merit, sacrifice, etc).