Oh, why do people have to be like this? I can't understand their reasoning. I don't know what to tell you, but you are fully right, of course. Don't let them take too much "power" on you, because then it will be even more difficult. You did right taking your son back, there is no reason that he spends more time than the week-ends at their home. And for the car, it's amazing! If they are in such pain, the first thing they think about should certainly no be about trying to get some money from it!