Do you have a place to stay or did you just "leave"? Ideally it should have been something that you explained to your D7 before hand, and then implemented later. That way they don't have the trauma of a parent just up and leaving.
Now you need to develop a plan of custody with your wife so that you can spend time with D7. Even if it is only ever 2nd weekend, make sure that there is a set schedule when both you and D7 know that you'll be able to spend time with one another.
Beyond that... if the fighting at home was bad enough then you ought to initially enjoy the respite. Enjoy the time to just sit and relax without have to walk on egg shells or get po'ed just by looking at someone. You'll have to GAL for sure now when you are away as you'll need that to fill the void left by your family & home. Sleep? It will come, you just have to find peace within yourself.
Just know that not wanting to subject a D7 to constant fighting between parents can be good. Let that help move your towards peace.
