Not to put too fine a point on it, but this line:
She isn't following through with what she said & that she is manipulative.
about the AP and this one:
He did admit to some TT & I told him we had to get it all out in the open because I wasn't able to trust anything he said.
about your WH describe both of their behavior as "not following through on what he/she said and that he/she is manipulative."
Your WH committed to you when you two married. He didn't follow through on those vows.
She is being manipulative. Your WH tries to manipulate you through TT and inaction.
If I could be so bold as to give a homework assignment, undertaken at your discretion, point out the similarities to him and then ask him what the damned difference is.
You might also light a bit of a fire under his ass if you gracefully point out that from all that you've read so far, healing from this is likely to be a 2 to 5 year job for you. Further, if you decided to D right now your healing would start right now and proceed in a predictable path. If, however, you choose to give him _your_ _gift_ of a chance to R and he screws that with the same vigor that he used when screwing AP, well, your healing will start over again with each new screwing.
Tell him that _that's_ what TT means because each new TT is a new DDay. Let him know that _should_ you decide to offer him the gift of R that you'd better already know everything because any TT, any lying _about_ _anything_, any hiding, even any suspicions that you have that are well-grounded, will be a new DDay for you.
Around here we say that Open, Authentic, Trustworty, and Honest communication (OATH-style, and a good mnemonic) is a requirement for R.
Open - if he has a question, issue, or whatever, he _volunteers_ this openly, as do you.
Authentic - No lying, no hiding, no blameshifting, no TT-ing. More than that, this ties in intimately with Openness. "WH, do you want to go to the hair salon with me? HIM: Really, no, boring for me. But I will happily go and read a book if you want me to."
Trustworthy - Trust is re-built with openness and honesty over time. Repeated, consistent displays of open, authentic, honest behavior are required for you to begin to believe that he might be trustworthy.
Honest - Do not lie, hide, or spare the BS or WS feelings by telling "white lies." All of those are out.
Regarding his IC - he should be planning to invite you to a meeting. Here in the U.S. he can sign a release (as can your IC) so that the two ICs can talk to each other. If he's lying or minimizing (lies, again) to his IC then your IC can catch that. Further, the two ICs should agree that both of you are ready to begin MC before you begin. Also, he can release his IC to talk to _you_ about _him_ when he's not present. His IC won't be counseling you -but- you can make sure that the IC is being told the truth. Bring evidence, it might be needed.
Regarding OATH-style communication - OATH-with-reservations might be appropriate right now from you, your decision. You haven't yet decided to offer R to him so you are not morally or ethically obligated to be fully open, transparent, honest, all of that. You haven't decided if he's the enemy, yet, or if he's fully trusted and you're all-in to fix it. You tell me things, for instance, but you wouldn't tell me your bank account numbers. Nor your income level. Think about how revealing what you decide to tell him will benefit _you_.
Don't threaten but don't pull punches. Saying, "If you don't do X by Y then I'm leaving!" is only effective if you actually _leave_ if he doesn't do X by Y. Whatever you say that you'll do you'd better do or he'll learn that you do not mean what you say and -that- will result in him not believing what you say.
There's a thing on here, "we teach people how to treat us by what we accept." If you teach him that your statements are hollow then that's what he'll learn and he'll take advantage, all people do this, not just him. If you were to say to SI, "SI, I'm leaving him on Thursday," and then don't leave on Thursday we learn that you don't mean what you say.
If you blindly take him back, forgive, rugsweep, minimize, every time that he has an A then you're teaching him that it is okay for you to have an A. If you cry and wail and he promises the moon when he has an A then he learns that he can smooth it over every time after you cry and wail if he'll just promise the moon.
Boundary. No more A's, ever. Consequence. You leave???
Think about this stuff, as I know that you're doing, and grow.