I'm so sorry, undonelife. It seems pretty clear that among all the rage and disbelief is such heartbreak. I want to preface my response by making it clear that it comes from my own experience, and from many years farther down the road than where you are currently standing; it may not apply to you or anyone else, but it's all that I know first-hand.
My H nearly killed me and our M with TT and lies, particularly during the year-long false R and for about another 8-12 months following the second Dday. Obviously that meant very little during the false R because the greater hurt was the very fact that he was still in the A; lies and TT are an intrinsic part of any A. However, during our genuine R, after Dday 2, the lying and TT were the factors that nearly ended us. But...I've come to realize that at least in my case, while all forms of lying were unacceptable, they were sadly rather typical. They were also long ingrained patterns, practiced and finely honed throughout the 2 years of the A. Even prior to the A, I think my H sugar coated things that he felt might make me anxious or worry me, all in a truly misguided kindness to make my world as peaceful and lovely as he could. So, given over 20 years of well-intentioned hiding unpleasantness from me, followed by 2 years of purposeful malicious deceit during the A, it really was not too surprising (in retrospect) that he continued to lie and TT me in the early days of R. He had to extinguish some well established habits and learn new patterns of communicating with me and with himself. That took some missteps, corrections, and time.
My H and I stayed in MC and IC for at least a year following the second Dday. Among other things, my H worked on his "whys" and learning new ways to think about himself and M and to communicate. I spent time working on communication and self-healing. I learned how to more effectively talk about the A, process my emotions, and to respectfully demand the truth from him--he learned how to provide it. Granted, there were no huge lies uncovered after our second Dday, but there were several instances of TT that could not be tolerated or continued (and like you, some of the lies/TT's were enormous in the feelings of betrayal and pain they produced, but none of them pertained to broken NC). Our MC was wonderful in helping me learn to determine if those lies/TT's were "dealbreakers" or were "setbacks." Dealbreakers meant our ending; setbacks meant pain, anger, and commitment to work through it and course-correct. Obviously we worked through it and are fully R'd now.
Sometimes the TT/lies felt insurmountable in the moment, as well as for a few days following a discovery, but with work, commitment, practice, honesty, communication, and Time, we successfully got through it all.
One final thought: I too felt like "my whole marriage had been a lie," but as time passed, and some healing occurred, I realized that was too broad a statement for my life. I had over 20 years of a M that was pretty damn good, not perfect, but solid and good. During that time, we had thousands of hours of love, laughter, family-building joy. None of that was false. My H was a fine man, and a kind and wonderful spouse and father until the A; then he was perhaps one of the most unkind and deceitful people I have ever known. I trusted that the man in the A was the anomaly, not the man I had married and lived with for over half my life. It may be helpful to try and determine who your H was prior to his A; was his behavior and treatment of you prior to his A similar to that during and following his A? Which man has he shown more of a return to--"pre A man" or "post A man"? How does he respond when a TT or lie comes to light now? Does he help work through it or does he minimize it? Is he working to realize the true damaging effects of TT's and lies of omission/protection? Do you want to spend more time and effort working on these issues or has your fury, frustration, patience, etc simply exhausted you and you want out (it's ok either way)?
Your recent discoveries are fresh and so very painful. Of course it feels likes a second Dday, and your healing is re-set to the beginning. It must all feel like a tragic waste of time and emotional energy. Perhaps it is, but perhaps not. Take your time to process it.
Oh, and before I forget, I do hope that the other BS knows about the A; whether you forward the stuff you have recently discovered or not, he should know about the A. IMHO, if he already knows about the A, I probably would not send this stuff to him as it just opens up contact again. Take care.