Lou, I rarely post these days but I have been following your situation.
There are two strategies that I wold like to suggest.
1. to engage with him, in a really interested and non confrontational way, about what he means by falling out of love and being in love. Do not put your point of view, but just get him to explain what he means.
You can use phrases like 'help me to understand' (or whatever works for you). Avoid 'why' 'what' and other direct questions. People love to talk about themselves, if you approach it right, and though it might be painful you will almost certainly get some insights. You might even make him think as well, if not now, later.
2. Take something away that he wants: in this case he wants to keep his options open. My guess is that he doesn't want to lose you, but he has no insight at all into his state of mind (depression) and like all MLCers they are in survival mode and think only of themselves.
When you have had conversation (1) you can say really pleasantly, that this situation isn't working for you. That you love him, but you need to focus on you and your life, and that he goes away and sorts himself out. Offer to be his friend (if you like) but make it clear that for you, life is going on and there is no more sitting around waiting for him to make up his mind.
Honestly at this stage you have little to lose, imho. If he isn't going to work on the marriage (and MLCers want it oh so easy) then the greater probability is that this is going to happen further down the line. From all that you have posted his foray into other lifestyles/relationships hasn't worked so far, but that he isn't yet certain that he wants to commit to you..
However, he still isn't thinking of you primarily (which he needs to do) and in the comfort of a 'trial relationship' in which he may 'decide' it still isn't working, he will get the notion into his head that coming and going is OK.
Sad to say this site is littered with boomerang spouses who think a revolving door is an acceptable way to behave.
In their hearts, people respect those who are kind and firm. Think of him as a mix of toddler and adolescent. But you are not his mother, and I have come to believe that clear rules of engagement and boundaries work best.
Please disregard this advice if it seems harsh or lacking in understanding. I actually feel very deeply for your situation, and am far from certain that your husband has any inkling of what a selfish and risky way he is living his life.
