I think he's in mlc from what you have described about rational thought and then the depression and his irraitonal thoughts/behavior. Well, it's possible that he could love both of you, but in different ways. He's torn right now and trying to figure out what to do. He may love you as a friend and she's his fantasy or should I say his "soulmate" in mlc.
I know this hurts terribly, but he's in mlc and there's not telling on any given day what will come out of his mouth. Sometimes they think out loud and other times, they'll contact you via phone or text and tell you things. But, no matter what, you have to say strong.
He needs a lot of space to figure things out. It may even come down to him moving out and getting a place of his own. If the ow does move in w/him, she'll be in his face 24/7 and that wonderful fantasy life will come to an end much sooner when the old routine of day-to-day life starts to creep back in. Whatever you do, do not move out. If he thinks life will be better out there in the wild blue yonder, then he should go.
There is nothing your can do to fix him and his problems, because you didn't break him. This is his journey and unfortunately, you weren't invited on it. Be glad you weren't because he just very well may act out even more. Keep a close eye on your finances and think about your joint accounts and credit cards. They do tend to love spending money when they start to enter replay.
I would suggest you sit quietly and be patient. The less you question him for now, the better. In fact, if you don't question him, he may just open up and give you more information.
Dig deep for patience, buckle your seatbelt and be ready for a ride that will have lots of bumps, twists and turns. This is a marathon, not a sprint and it will last quite a while.
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.
