Here is a link for you, a very good description of midlife transition as a predictable developmental stage, written by a psychology professor on his own website: "Midlife Metamorphosis" by Dan Johnston
Generally, people bring whatever baggage they have into the midlife crisis. Your account of your husband's early life sounded very much like the situation with my first husband. (It is helpful to have travelled this ground before, but a heck of a way to gain knowledge!) But this is not at all the story of my second husband's early life, and he is also having MLC. So my advice to you is to forget all of these ruminations and explanations. None of those details really matter. What matters is how you decide to respond to H MLC. How you respond to the present situation can make a difference in the outcome, BUT, but, but, but -- you have also to accept that even with the most enlightened response the outcome is not guaranteed. This is a true crisis in your marriage. It could go either way. All you can do is to play the best hand you can, give yourself whatever small advantage is available. AND ALSO, the best hand you can play towards preserving your marriage is also the hand that will preserve yourself regardless of what happens in the marriage crisis. This is a big deal, a lot going on, a lot to think about.
My advice is -- do not, absolutely do not try to get from H anything about what his plans are, or rational planning for the future, or reassurances about your relationship. Right now, all is chaos in his mind. All there is are a bunch of regrets and possibilities. He is totally consumed by his own inner process. He is unable, truly unable, to factor your wellbeing into his thinking. You are much more stable and competent now than he is. If you force the issue which naturally consumes you: what is going to happen to my marriage? -- you may end up forcing him into a position which you will not like. So learn to live with this chaos and work on the little things which may eventually result in the H chaos organizing itself back into a life with you.
As far as obtaining from H a contact schedule which suits YOU (and why not, Brita, after all you are important in your own right, and you are also important to H healing, so no need to be apologetic about this) -- it is a matter of delicate negotiation. Demands will not work. First of all I would let H have a chance to feel comfortable and nurtured in your presence -- replace embarrassing questions/concerns with gentle validations and gentle fun. Then I would simply and gently let H know that you have a life -- you can't be on perpetual hold for him but you really do want to see him and don't want to miss a chance to be with him, so you would like the two of you to work out a schedule of contact. Go for the minimum contact which will allow you to be comfortable -- he does need lots of time to himself right now.
It will likely take more than one session to arrive at agreement. During the negotiations, make it clear to him that you are happy to give him the time & space he needs right now, but you will not tolerate sexual infidelity while he is living apart from you. Gentle but firm.
Read everything you can about male midlife crisis. Jed Diamond is one of my favorite sources. He's written a couple of books and blogs on-line. Do a google for his on-line articles.
This takes a long time, be prepared for a long haul. Try to enjoy the ride. Best of luck.
