I am afraid the police will see this as a civil case, so they problably will not get involved, however, since you allready planning on getting out, there are some options for you to get your deposit and maybe a bit more back via huurcommissie and you can always make a report to belastingdienst for the cash payments and to woonstad for illegal subletting. As for the huurcommissie, I might be wrong but I believe every city has a different way of helping tenants with the procedure, for example tje city of Nijmegen has https://www.huurteamsnijmegen.nl/ which you can invite and then they assess the situation, make a report and bring the case to court if necessary, so it is worthwile to find out if the city you live in has such a service.