He doesn't have sexual feelings for you because he's in mlc and that means depression. Depression is playing a huge role in his life right now. Many will say that their feelings for us are dead right now or there is not interest in having sex w/us. He's not looking for a deep sexual relationship w/anyone right now because those feelings are just plain numb. Depending upon where he's at in his head, he may meet up w/someone and just have "sex" whereby there is no real connection, but just blowing off steam, i.e., it's just the act of having sex.
Keep in mind, teenagers and young adults go about having sex and in many instances, it's just a bodily function that requires a "quick fix" and no deeper feelings involved.
So, I would just file that comment away because the depression really does take a toll on their mental, physical and emotional state of being and right now, he thinks that his problem is the relationship he has w/you...but technically, it's not. It's all about him, his visit back in time, childhood issues, etc.
Depression is about things of the past and anxiety is about things in the future.
Ambivalent, he's not ready to let you go. My question to you is this...are you ready to let him go? Are you ready to drop the rope and give him all of the space and time he can choke on to find his inner "self"? Or, are you ready to call it quits and move on w/your life? I personally think it's worth giving him more time because you've had a long relationship w/children and there are many, many good memories that were made. Let me rephrase my question...if your h had cancer or some other disease that was slowly eating away at him, would you toss in the towel and call it quits?
No matter what I've said above, just remember, only you will know when you've had enough and want to end your marriage. I'm here for you no matter what you decide to do...but I do think you need some time to truly think about things and not react w/a knee jerk reaction. Just my two cents.
Sit quietly, the answers will reveal themselves when you least expect them to. The past is gone, the present is a gift and you need to focus on today, allow the future to reveal itself when it is ready.