He is frightened and he wants to go back into the womb (of his biomother) and start over. He's given himself over to a witchdoctor/shaman who (I hope she's an old crone and not an attractive sorceress) seems to prefer her recipe for him to undergo a magic process--like a death and rebirth--before he can rejoin the life he led before with no knowledge of WHO he really is (because his family of origin was unknown to him.
But the problem with her approach is that she's using intuitive skills to visualize FOR HIM what he needs to experience, and that means she has taken his discriminating ego, moral judgment and will power away "for the duration" of her treatment episode. A Jungian shamanic approach would make use of HIS OWN DREAMS (and thus HIS OWN IMAGES rather than HER imaginary SOULS, whether they are really dredged up from her mindreading of him or not) and empower him to discover his own forward-driving impulse toward personality development.
I'm aware of a delicate batch of issues here, because on the one hand, his remorse over cheating is a very good sign; but on the other hand his psychic guide seeks way too much power over him, clearly knows far too little about psychodynamics, and yet wants to eliminate the influence of your love and his love for you (which he admits has not gone away).
I've considered instructing you in how to "hypnotize him" from a distance (that is, through psychic influence), because that is both possible (especially if the target person does not WANT to resist it) and morally defensible, since you both have a long-standing love for each other, so you would not be implanting a love that sneaks under his defenses and sabotages his own will.
But this psychic therapist ("holistic" doesn't work as a label for me, except to imply that she uses her own mix of "New Age" methods) would be likely to sense and possibly combat that influence, because it might rival her own efforts to "heal" him. And my own moral sense recoils from psychic wrestling with an occult-leaning self-proclaimed therapist (does she have a UK license to do anything?) over the soul of a man who has not sought my expertise.
So I'd advise you to 1. investigate the credentials of this woman. I've dealt in dream interpretation a few times with women in the UK whose spiritual practices put them on the fringes of society, who don't follow the limiting guidelines of the Christian churches, and use their mindreading skills and esoteric studies and visualizations to "treat" people whose psychological problems are not being approached within the primitive but communal traditions of organized religion, OR the far more intelligently developed traditions of the schools of psychoanalytic, Jungian, neoanalytic or newer, more superficial schools of psychotherapy. Such enthusiastic but lopsidedly undertrained shamans aren't the only therapists that can do more harm than good.
And a second practical advice: If anyone moves out of your house, it needs to be HIM and not you. For he should FEEL the nostalgia (means pain for the nest) for what he's giving up to pursue this woman's program for him. I advise you to remain completely firm on that assertion: If he wants to follow this woman's guidance to "find himself" (even though most of himself is already present in his present container) then it is he who must depart from his nest to carry out this symbolic quest.
Paradoxically, the symbolism of him leaving home, like the thousands of folk tales and filmic hero-quests of yore, could actually HELP him find out sooner that he already knows where he belongs and who he belongs with. And you could suggest that when he wants to return home, the two of you should see a trained and certified Emotionally Focused Couples Therapist for a few sessions to reknit your emotional intimacy together. Those therapists also know a comparatively simple emotional process for concretizing his REMORSE over the one sexual betrayal, so that he can feel the full extent of his guilt and empathy for you, and you can know that he's ready and worthy of your trust again (tho I think you already know that--but he doesn't).
With all this said, I can agree with his guru that he's soul-dead; but that's mainly because it's quite common for both men and women to have completely lost track of the need for a soul-development (or personality development) track in their lives, even if they still have a wishywashy religious affiliation, or a rigid set of beliefs under which they are doing everything it takes to get into heaven when they die.
Among Jung's many great contributions to human psychological development is the discovery that the first half of life is meant for breaking the umbilical chord and "graduating" from the family of origin and then establishing a home and financial base of one's own, and the second half of life is meant for discovering all of what's inside of oneself that has been neglected in favor of the struggle for fullfledged membership in the external world. So one of Jung's popular books was called "Modern Man in Search of His Soul." So your holistic therapist might even preach some truths that come from Jung, and might use Jung's discovery of "active imagination" (and even art therapies) as tools for development of this neglected aspect of a "holistic" personality.
That leads me back to my previous suggestion that developing your own awareness of where your unique life path needs to lead you, through reading and dream interpretation, would help you gain your OWN footing on a life path, so 1. you're not unconsciously depending on your love relationship to be your only or main source of meaningful process and progress in life, and 2. you will have your OWN excitement for new personality development that can inspire your husband to realize that you are not JUST the "helpmeet" that has always been at his side, like Adam's rib, but you are an undiscovered person in your own being who can lead him as well as follow.
It's even possible that you married a man who didn't know where he was coming from because you didn't trust yourself to explore the unknown outer dimensions of your world--you needed him in order to venture forth from your family of origin with enough sense of safety. Now your learning to drive means navigating into your unknown outer world, and your inner world needs to unfold as well. To "spark" his interest, you may need to awaken your own "spark" and that might include entering a safer (than that woman's probably undertrained and unsupervised) form of personality development.
(I'd recommend Jungian analysis with a woman--so you don't risk developing a romanticized feeling connection that could mirror your husband's danger. Jungian analysis is a pretty strong school in UK.) And if you've had any recent dreams, you could send them to me on the Dream Interpretation site here, where I could explore one or two with you to see what they might indicate for your prospects of entering into a phase of your own self development.
In my textbook "Love and Intimate Relationships: Journeys of the Heart" (2000) I cover in six pages (353-358 if you can get the book) what happens when I couple remains static in their union stage or "we-ness" which you may have done in part because you haven't been able to have children that would have forced you into new modes of action and relationship. (I could scan, but I'd have to use "Additional Services" (probably) to get to a venue in which I could upload them to send to you). Doing things separately is not frequent, nor does it lead to development of unique parts of each partner's personality that wouldn't naturally fit into the initial way they function together. The energy in relationship can stagnate and one or both can feel smothered, though they may be unwilling and unable to admit that to themselves. This can happen around the age 30 crisis (as it did for me and my first love), but for you it may have happened around the age 40 (midlife) crisis. (I know I'm guessing here, because I know almost NOTHING about you. But it's worth considering.)
In a book by Bader & Pearson "In quest of the mythical mate: A developmental approach to diagnosis and treatment in couples therapy" (1988) the psychodynamic authors work from the fundamental principle that both partners need to continue their individual growth AFTER they have grown together as a couple for a few years (normally childbirth forces some of that), and that this "differentiation of oneself from one's partner" and from one's expectations that "soulmates" means that we think and feel alike and want all the same things forever can be quite painful at first. That is UNTIL they discover that needing to adjust to your partner's personality development repeatedly over a lifetime of building wider and deeper ramifications of who you are is a fascinating process that rewards disappointment, conflict and difficulty with new love over and over again.