I feel for you. when I worked in air ambulance maintenance I worked the kind of hours that you have. My biggest complaint was that I didn't have predictable time off. That would be even more of an issue with two small children. I have always heard the saying 'You have to have a job to find a job'. If you aren't happy, start looking. The look on your employers face when you tell him you are leaving - priceless.
Remember that the one who looks out for you and your family is you. If as you say it is affecting your family life, move on.
Good luck with whatever you decide.