Regarding Question 1--Can sacred magic be Christian?--I've tried to share what I think is the best case for an affirmative answer. Of course, you don't have to find that case either orthodox or convincing. It's just the best case, I think, that can be made.
In making that case, I've offered different descriptions of sacred magic. The major one has been theurgy, sacramental practices and rituals that make material reality receptive to divine energy and power with a goal toward union with the divine. Critical to distinguishing sacred magic from sorcerous magic is that the practices and rituals of sacred magic are not an attempt to manipulate or control, they are, rather, practices of attunement and subordination to God's will. In sacred magic, the prerogative and initiative of God is never encroached upon. In rituals of sacred magic, we become passive, expectant, and receptive to the actions of God. The goal of sacred magic is union with the divine and bringing material reality into conformity with God's purposes. "Not my will, but yours" and "Thy kingdom come on earth, as it is in heaven" are its guiding petitions.
What are these practice of sacred magic? They are the regular practices of the Christian life. Prayer, study, contemplation, liturgy, the sacraments, spiritual disciplines, and righteous action.
This brings us to Question 2. Of what value it is to describe sacraments, prayer, liturgy, and moral deeds as "magical"? The argument I've made is that describing practices as theurgic is different from describing them as moral or symbolic. To describe an act of kindness as theurgic, for example, is to describe a healing power flowing through a person and into the world, a power that is ontologically repairing the world and changing the person on the journey toward divinization. Kindness isn't merely "good" from a judicial perspective, it's attunement to God and becoming a receptacle of God's power and presence in the world. The same goes for any spiritual practice, from going to church to fasting.
Simply put, describing Christian practices as theurgic highlights their ontological dynamics, the interaction of the material and spiritual realms. The categories of the "moral" and the "symbolic" keep spiritual reality "at a distance." Theurgy, by contrast, describes how material reality can become interpenetrated and united with spiritual reality in a way that changes, transfigures, and transforms material reality.
Having said all that, do we need the category of theurgy? For example, what I've described as sacred magic in this series is more generally understood in pneumatological or sacramental terms.
For example, where I've used terms like "divine power" and "sacred energy" most Christians talk about the indwelling, activity, and power of the Holy Spirit in their lives. I'd suggest that theurgy captures how most pentecostals and charismatics describe their experience of the Holy Spirit. The clearest illustration of this is the laying on of hands in healing prayer in the expectation of a miracle. More extreme examples of this are faith healings. Relatedly, as I described with Kabbalah, we also see evidence of how the sacred magic of pentecostals and charismatics can tip from the sacred to the sorcerous with the Christian prosperity gospel. Instead of attunement and subordination to the divine will, the power of God is called upon to satisfy desires for heath and wealth.
To be clear, I'm not bringing up pentecostals and charismatics to throw shade on sacred magic. I'm bringing them up because pentecostals and charismatics highlight the overlap between pneumatology and sacred magic, for good and ill. The good part is how the Holy Spirit infuses our material reality with God's presence and power, often in miraculous and magical ways. Pneumatology is often theurgic, the location of sacred magic. And, to turn to the bad outcomes, it's precisely because of this overlap between pneumatology and theurgy that pneumatology is chronically tempted toward the sorcerous. Just like what we observe with the prosperity gospel or Christians who become obsessed with "acts of power" given by the Holy Spirit. This is the temptation of Simon Magus in Acts 8.
Beyond the pneumatological, the other place where we observe the theurgic is in the sacramental imagination of Catholicism, from holy water to the Eucharist. Does the category of theurgy contribute to this imagination? I'd say not really if your sacramental imagination is truly ontological. That said, as we've discussed, Catholics are losing this imagination. Contra Flannery O'Conner, the sacraments are tipping away from the ontological toward the symbolic. Consequently, introducing and highlighting the theurgic and magical aspects of the sacraments can be a helpful intervention. If the word "sacrament" is coming to mean "symbol" words like "magical" and "theurgic" might do good work in brining the ontological realities of the sacraments back into view.
In addition, introducing the category of sacred magic might also help explain to Protestants what they find so strange and spooky within Catholicism. From the healing powers of relics to cleansing objects with holy water to warding off dark powers by making the Sign of the Cross to the protective power of the St. Christopher medal hanging from the rearview mirror, much of popular Catholic piety are practices of sacred magic. These practices are generally sneered at by Protestants as being, well, too "magical." But if sacred magic has a proper place within Christian life, some of this Protestant antipathy might be overcome.
And finally, we come to the burning issue of Question 3. Would it be wise to start describing aspects of Christian life as "magical"?
In my opinion, no, not widely so. In my estimation, the category of "magic" is just too controversial in Christian circles. Any attempted introduction would be too much of a bother to be worth the effort. I'd never refer to "sacred magic" in my own church context or out at the prison. "Magic" simply means "sorcery" in Christian circles. The idea of "sacred magic" would sound oxymoronic. If Christians can't tolerate reading Harry Potter, just imagine how they'd react if you described prayer as "sacred magic."
That said, as we've seen, theurgy is a term Christian theologians use. And they use it for precisely the same reason I've done this series and wrote Hunting Magic Eels: the re-enchantment of Christianity. I think I've shown in this series how describing something as theurgic, in contrast to moral or symbolic, is illuminating and helpful in the task of re-enchantment. Simply put, "sacred magic" brings the ontological aspects of our spiritual lives--from kindness to prayer to the Eucharist to baptism--into view. When we describe something as "sacred magic" we mean that something is "really happening" right here and right now. Without this theurgic vision, that something is really happening, Christian life becomes sentimental and moralistic. Just vibes and politics.
To conclude, I think the only place you could speak of "sacred magic" is among a group of fellow-minded Christians. Perhaps a person like you, dear reader, if you've made it this far. Others will elect to take a hard pass. Regardless, I appreciate your willingness to think non-anxiously outside the box during this series as we engaged in a bit of experimental theology. We've hunted for some magical eels and we've done some good work in keeping Christianity weird.