FIrst, this is TRAUMA. I spent countless hours w/ an IC who represented herself as specializing in infidelity....and made VERY little progress. What helped me the most was an IC who specialized in TRAUMA.
Most CSAT (certified sex addiction therapists) now work from the relational betrayal trauma model, so a CSAT should be in a position to treat the trauma through the lens of infidelity. Like any therapist, not all CSATs will "'click" with the client. The only CSAT in my area who takes my insurance is good, but has a personality/demeanor that I find somewhat cold or distant, and I don't think she pushes me hard enough. So, I see an IC who specializes in trauma healing. Started with neurofeedback, but she also does EMDR and IFS (internal family systems) therapies. She's been a Godsend to me. It's difficult, hard, soul pounding work.
Everyone is different, and we MUST keep in mind that the BS brings their own emotional baggage to the table that is dday. What the particular baggage contains is unique to each BS.... FOO, abandonment, past sexual trauma, etc. All of those old wounds can be reopened by dday, so the BS is not "just" coping with the new (and giant) wound of sexual betrayal, but may also be coping with the feelings of all the betrayals and hurts of the past. For me, it meant that tons of IC work I'd done in the 30+ years before dday basically went out the window. Every damn scar from my life was now also in need of cleansing, sutures, and time to heal. One of the tricky things is finding and identifying all of those old hurts and how they impact the new, giant, wound in my heart. It's about as fucked up as anything can be.
I also want to comment on the books you list, but particularly in conjunction with the idea of the relational betrayal trauma model. One of the tenets of RBTM is that BS can be re-traumatized by the advice/therapy they get after dday. A common one is being labeled codependent. A BS' trauma response may look like CoD behavior, but it's really a trauma response that is triggered by dday. Personally, I had CoD tendencies before dday, so that label wasn't particularly retraumatizing for me, but it can be for others who did not have CoD issues before the trauma of dday. I bring it up also bc when the message a BS receives post dday is there is something wrong with them, it can be another layer of trauma (and I think most of us intuitively go through a period of thinking it's somehow our fault, we aren't enough, etc., making it a double whammy). That message almost always comes from a WS. But it can also come from an IC/MC. And in my experience, there is ZERO question in my mind that it can come from any number of the plethora of books out there on infidelity. I have a 2-ft tall stack of infidelity books - and those are only the ones I had to buy bc my library didn't have them... if I added the library books it would probably be a 5-foot tall. And out of all of them, the only ones I got real benefit from were How to Help your Spouse Heal From your Affair, and Not Just Friends. The rest may have had a some useful insights, but nothing solid. Nothing that resonated like MacDonald and Glass.
This may or may not be the case with your BS. I will say that for me, everything from Mira Kirshenbaum (which I didn't even read until year 2) felt like BS blaming. I don't have the books in front of me to quote directly, but in at least two of the books there was stuff that basically said the BS needs to look at his/her role in the A. I don't believe that stance helps OR gets to the core of healing from the BS' perspective. It's like it skips steps. I do agree that a BS does need to dig deep into their own behavior in the M. But that part of it comes as part of R, or part of what s/he wants from a new relationship going forward. IOW, it doesn't address and process and heal the trauma itself. It's like putting a cast on a broken bone before it's been set back into place. It may heal, but not in the most effective and long lasting way.
Many books will use the term "vulnerability" and what made the WS "vulnerable" the A, and then looking at the M or the BS as one (and sometimes even the primary or predominant) source of that vulnerability. IMO that is utter and complete bullshit. The things that made a WS vulnerable to an A are the WS' own crummy coping skills, own sense of entitlement, etc. I think this is especially true of those who have LTAs or have multiple As/ serial cheating. To me, the problem with the language is yet another way to rope in a BS to accepting responsibility for the WS choosing to life a secret sexual life, choosing to lie to their BS, and choosing to engage in the A(s). another way to judge and pathologize the BS when s/he is in a headspace that likely needs the exact opposite.
Of course a BS has a role in M issues (tho I have never subscribed to the premise that it's 50/50, as no one can be 50% responsible for actions when their very reality is nothing more than quicksand). It just seems to me that delving into the BS' "role" in the pre-A problems in the M is an exercise that happens after there has been some solid healing on both sides of the street. Most BS will automatically blame themselves for at least some period of time after dday (and how much and how long depends on what's in that baggage we all bring to the dday table), so adding to that mountain can be counterproductive to the BS healing.
So, I guess the bottom line is be careful about the ways in which books and IC/MC can pathologize the BS in a way that basically increases the trauma. It can be very subtle or subliminal, but our lizard brains can pick up on that crap..
For me, one of the biggest lightbulb moments was listening to Marnie Breecker's 2-part interview on Duane Osterlind's "The Addicted Mind" podcast. There was a thread on SI with approved links, but you can google it. I was probably around 6 months when I stumbled upon that thread. One of the biggest gifts there was giving language to the things I was feeling, like it being an existential crisis (which it sure as heck was for me). It was the first time that I felt someone just understood what I was going through. Breecker and Osterlind have since started their own podcast, called Helping Couples Heal, that focuses on the relational betrayal model. I recommend both podcasts.
Other game changers were Rick Hanson's Resilient, which is about finding and incorporating joy into your life, being a friend to yourself,etc. I still use his techniques. And The Body Keeps the Score by Bassel Van der Kolk. That book is solely about trauma. Again, it put language to the things I was feeling and many unhealthy behaviors. Validated what was going on and helped me to see that the fact I was not healing in the way I wanted was not bc something was inherently "wrong" with ME, but that it was TRAUMA, and trauma is some tricky shit to address and process and heal from.
I became a huge fan of Brene Brown, and have read and listened to just about anything I could get my hands on. I think all humans would benefit from reading her work.
This is probably pretty long. Not sure if any of it will be helpful, but this has been my experience.