Hope, I've only briefly followed your situation but it seems like you have one that has a hard time letting go and you harbor a hope for reconciliation.
This guy is offering to co-parent and wanting to review resources on doing so? I think that's huge. In many of the cases I've seen, and my own, they are unable to do any co-parenting and don't follow through on the lame efforts they do make. Given your child's young age, you are going to be at this for a long time. I would want that to be as civil and cooperative as possible.
I don't think you've identified the breach, and I'm guessing that maybe it involves an introduction to an OW, which I get would feel like an awful violation and even though my kids are much older, they've never met an OW. Whatever the infraction, find out from your attorney whether the law would even support you in enforcing it, because in most places I don't think it would if it is an OW, and you don't want to tilt about windmills over something you won't even end up with anyway, because you risk the loss of other things you might be able to bargain for.
In any event, why not use the branch he is offering as a means to frame the discussion you want to have. I think when you make demands and expect compliance in these types of situations, you stand to risk what you have: namely one of these guys trying to have a co-parenting discussion.
If you feel strongly that the breach would continue absent the discussion (and it did anyway with the agreement in place), how about suggesting that you are OK with not having the discussion of the past infraction (that these guys hate and will probably only result in monster and resentment), as long as he agrees that pending the co-parenting book/discussion plan that he agree to honor the agreement that you guys made before the breach, and that through that book/discussion/series of discussions, you guys can decide whether any modifications to it are warranted. This makes him a team member in the decision, rather than a sanctioned party
Going about it that way sets you up as mutually looking for agreement rather than being a finger-waving mommy type that nobody takes well.
