Starsky, according to what she has written, he doesn't know that she knows.
and she doesn't "know" anything definite either, just a lot of suspicious things (e.g. that he is skyping a lot of people and is very secretive about it) that indicate that he is probably involved in at least an EA, maybe more than one.
but this isn't the only thing going on. she writes: "Am getting mixed messages from him. He is planning for our future but says anywhere from 2 to 6 years down the road he is divorcing me. How does this make any sense?"
and: "I guess this is an MLC. He is drinking an enormouse amount as well and keeps telling the kids and I what a waste the last 15 years have been and how much we have held him back. Has no problem telling kids this either. (Note: we have been married 18 year - 15 years is the amount of time we have been in the US since moving from UK.)"
therefore this is just one of many symptoms; he seems to be in MLC where he is "trying out" a lot of inappropriate things, the EA with strangers on the internet being just one of them. confronting him would not stop him, but instead his response would be to justify what he is doing - and once he puts these excuses into words, he is justifying it not only to her but also to himself, which could turn a temporary situation into a more permanent one.
just like with the drinking - you think he doesn't know it's wrong? but if she confronts him and tells him to stop, would he do that? instead he would make excuses (probably blaming her) and in doing so would convince himself that his behavior is justified.
therefore I think that at this stage it is more prudent for her to GAL and not confront, not to let him know what she knows, and see if the infidelity will wither away on its own, as many of them do.
on the other hand if it would ever become more serious, it would also become more obvious, and that would be the time to confront. however, he might never reach this stage, and if she is successful at the DB techniques, he might get over the MLC and realize that what he has at home is worth a lot more than anything outside.
