The problem here is that jws are strongly discouraged (forbidden) to sue another jw. While each congregation is self-insured through the WTS, it seems to be for specific things. Since the elder was acting on his own and not as a rep of the WTS, suing the congregation may not be possible. Suing him as an individual could bring pressure from the BOE. Is it possible to get this elder to make monthly payments set up legally (see an attorney). Were they any eyewitnesses to the accident or his taking the keys from you?
*** w78 6/15 p. 9 The Sermon on the Mount—"Do Not Resist Him That Is Wicked" ***In agreement with this counsel, the apostle Paul wrote to Christians at Corinth: "Really, then, it means altogether a defeat for you that you are having lawsuits with one another. Why do you not rather let yourselves be wronged? Why do you not rather let yourselves be defrauded?" (1 Cor. 6:7) Yes, they should have been willing to suffer personal loss rather than to see the congregation’s reputation hurt publicly by some controversy at court.