If they’re not paying you for your work, they’re not your employer they’re your slave master.

OP should tell his “employers” that they can either pay what they owe for work he already did immediately, or he can take a paid vacation for the amount of days he wasn’t paid for, or they can handle it in court. Those are the only reasonable options. Hell, OP should charge them fucking interest for every day late it is. They’re effectively giving themselves a loan with his money in the most charitable interpretation of their behavior.