My h was like this too. WMD- my experience exactly.
They work this hard because they want to. It is about lack of self esteem and undealt with issues in themselves.
They usually have the 'aholic' tendencies as well- in case of my h, it was 'passionate interests', as he used to term his many consuming hobbies when he was here. Of course, that finally led to another one, namely collecting hundreds of women on the net for sex conversations, which he denied for years.
And now he says it was how he dealt with the work related stress. Because, if work is good, that is how they get their 'fix'. If it is bad, eg the dangled carrot doesnt work out this time (that happened to my h on a couple of projects) they need it from elsewhere. He times the OW starting to work project he didnt get.
I have lived your lonely life, once. It will continue for as long as you let it.
Look at it this way- and please take away the 'he is doing it just for us/money blindfold just to consider this- he is intent on meeting his needs, but quite able to ignore those of you and the children.
Sorry if that is harsh, but I would give anything to help another woman avoid what I went through, and you are already getting there. It gets WAY worse when you finally see, years down the line of lost family occasions, that it wasnt this reason or that, this job/project/boss or the other, it was just him and his own needs.