Hey Lemonman,
Ok, this may sound odd, but in the "old days" more than a few people came here because they had "fallen out of love" and at least one of them wanted to rekindle what was there. My situation probably fell into that category.
First, I am not suggesting that you act as their counselor. But what you need to do is ascertain whether or not both of them WANT a good and fulfilling marriage? If that is the case, and it sounds like it might be, then separation is not the right move. But, more importantly if they loved each other before then can get it back.
I would strongly urge them to consider counseling with the Harley's. I would strongly urge them to read Fall in Love, Stay in love, or His Needs Her Needs primarily to familiarize themselves to the lingo, and the fact that recovery of their marriage is very possible.
It takes learning to speak the same language. It takes realizing that they can in fact change things without having to change themselves. Perspective is what needs changing.
My recommendation to them would be to call the Harley's or someone very much like them. I would also suggest that you go out and buy two copies of one of the Harley books and give it to them. If you can sit down with them face to face and discuss why you are giving them these books and that there are ways to rebuild the marriage, that is better.
Don't be their counselor, but guide them toward where they can find the resources they need. It is amazing how little most of us (this sure includes me) really know about the mechanics of a marriage and relationship. Worse we know very little about how to rekindle one. Most assume once dead, it is dead but in relationships this is not true(probably a huge mental change for someone that has to deal with people dying all of the time.)
So check to see if they are willing to try. If so, guide them to the resources they need. That is my recommendation.
God Bless,
JL