With the "no fault" the A isn't an issue
It might not be an issue, but it might be a bargaining point or it might just end up being something that _you_ want as a consequence for him, if you decide to D.
For, if you D and if you file first _and_ if you put Adultery as the cause on the D filing then that will forever be part of the record. Where I live those D records are public records -and- they're searchable from the internet. Further, folks on SI recommend looking up public records when we start dating after a D.
So, the net result would be that any woman that he asks out would look him up, find the D, find that you filed it on the grounds of Adultery, and perhaps think twice. Or at least be forewarned, eh?
is this an aberration or is it going to happen again?
One can never know, can one? It becomes a question of faith, and the ability to have faith and to trust. He's only in control of his end of it (and we might wax philosophical on that subject, later, if you want) and you're only in control of your end of it.
By this I mean that he might truly learn, grow, and change (though change is hard work), and become a safe partner for you. You might, on the other hand, never believe, never _trust_, that he is a safe partner for you. Or, he might go to IC and read and never change at all and _you_ might decide to trust again and be hurt again.
At some point you're going to have to sit down and wrestle with this very issue. Do you chance it again with him. Are you mentally able to, do you have the emotional makeup and wherewithal to? Read in the Reconciliation forum for what giving the gift of R to him looks like with various folks. Apparently the anger hits in Year 2, and then there's the Plain of Lethal Flatness (in emotional response of the BS), and there are other challenges.
If you decide to try to R you might find out, part way through, that you just can't. And that is okay. Disappointing, but okay. You will find out about Transparency, where he has to (and, really, has to want to) give you all of his email accounts and passwords and such and be accountable for his time _and_ be willing, even eager, to take a pic with is phone of where and who he's with and text it to you at any time. And you'll have to understand that there are circumstances, like business meetings, or driving (where phone use is illegal in some states), or pooping, or a performance review, or whatever, where he just cannot right at the moment. You might panic at those times. People do.
During all of this, too, remember that he's his own person. He might decide to file for D at any time. If he gets too uncomfortable, or too self-destructive, or whatever, either of you could decide to file at any time. You always could've, in fact, without telling the other until they're served. This is a fact of life if an unsettling one.
Back to the subject two paragraphs ago. You'll also likely find yourself in the position of Marriage Police. You will be checking all of the phone bills, and all of the credit card statements, and all of the bank statements, and calling or texting him and wanting pictures frequently. This serves a good purpose because you can compare what he _says_ with what he _does_. That's how trust is rebuilt. It can't go on too long, because you don't want to become a Parent and him a Child in interactions. (See the wikipedia article on "Transactional Analysis" for more of this model of interaction, the Parent-Adult-Child relationship model.)
Sit and think for a while about R and D. If you can't decide right now, that's fine (and actually expected). What you -can- decide is a date, say four? five? six? months from now to sit and review your situation again. Set dates to make actual, active decisions about D or R. What you don't want to happen is that you both become complacent and drift into a sort of unspoken, unagreed-upon, R without the Transparency and without being Open, Authentic, Trustworthy, and Honest with each other. That drifted-into relationship would pretty much be rugsweeping. You do not want to teach him that he can have an A and that you'll be mad for a while and then you'll both let it drift away and not speak of it.
He needs, as one thing, to get over his abandonment issues. He needs to get over being so needed that he'll have an A, whether EA or PA, to feel needed.
He needs to grow up.
A fist bump to you, sister in adversity. You have a long row to hoe. }{
thoughts?