How do you handle teenager and ex's disrepsect and lack of helping establish rules and stability?

My daughter is fifteen and overall a good kid. However, lately she ias been difficult at times. Her mom moved back to the area in January and as usual has been disruptive in things. Up until recently our daughter has lived with me pretty much full-time despite a 50/50 legal and physical custody. The reason being because my ex continues to move all over the city and out of state leaving my residence the only stability point. Now, I am dealing with the fact that neither our daughter nor ex-wife seem to feel it necessary to establish a set schedule of where she will be staying. The game of our daughter playing sides when upset being a determining factor of where she stays...when upset at me...she goes to her moms (her mom picks her up when I'm not home) When upset at her mom...I do not allow the same liesure...I explain that she needs to work through it...not run away. It seems even years after the divorce I am still the dad; laying rules, paying all the expenses and necissities while her mom pays the cell, concerts, movies, etc. only when she has the money to do so.

Any advice on how to handle or approach this situation. I cannot afford to pay for a lawyer to do this and would rather be able to reach an agreement on a more mature level seeing how our daughter will be sixteen in two months.