Me, if I was really pissed and convinced I deserved my property back, I'd just go get it, including whipping father-in-law's bellybutton if necessary. The consequences would be paying the $200 fine for disorderly conduct (I'd make sure there were witnesses that would back me up that he provoked me - its a Texas thing) and then since I now had possession he'd have to sue me to get the stuff back (probably defensible since ownership could be demonstrated by gathered evidence and testimony).
Thing is, if you're saying the in-laws were letting you stay there rent-free, why the hell are you upset? Don't you feel an ethical need to contribute?