Some of your story mirrors mine in so many ways. My wife and I two started off in that extreme infatuation phase like you spoke of. We have since had so many ups and downs. It can be so confusing.
Once he broke up with me on the way to dinner, then he apologized, then it happened during dinner, then apologized; then at the end of dinner walking to get gelato.
We too have had so many break ups and then back together, it can be exhausting. Once she told me to leave because she wasn't in love with me anymore, but then had me stay the night because she didn't want to be alone, only to kick me out again the next morning. Then a few days later apologized and made up. Then there was an affair, which we worked through and sought out marriage counseling. There has been many of what she calls "connections" that she gets with other guys. She tries to say that she just connects with them on a different level. We just recently had another episode where she said she was unhappy and has been for a long time, even though not too long ago she was saying how she felt like we were getting that passion back again. The we have a talk and she tells me how she could never leave me because she loves me too much, but just no "in love" and has lost all the passion, but that she wouldn't leave me because we have been through so much and I have done so much for her she feels like she owes me. To me that was kind of back-handed compliment, almost as if, I don't want to be the one to leave because I don't want to look bad. It can be so confusing. Then as of right now she is willing to work on us and keep an open mind. It can be exhausting. My one hope is, I have read many times that with therapy and time, it can get better. We had a long period of good not too long ago, even making the decision to have another baby. I get my hopes up that that other side of the cycle wont return, but it always does. I just hope we are able to get through this.
As far as suggestions, only thing I can do is talk from my experience. If your spouse is being volatile, I would step back and keep my distance until he calms down some. You also have to think about how he may perceive what you are saying, so keep it as clear and straightforward as possible. When I talk to my wife when she is like this, I have to keep it as clear as possible, because if not she will take it completely different as to how I meant it, and twist up and make it seem like I was attacking her or being hateful when that was never the case. I don't believe she does it on purpose either, she truly believes that's what I was saying, so I always try to make sure and clarify myself. But even then, she can take offense to that saying that I don't think she is very smart or I am talking down to her, which again was never my intention. You may want to seek counseling yourself. I have, and it has really helped just to be able to talk with someone and get validation that I am not just going insane.