I have asked a question that has no possible answer due to a flaw in the underlying system that hasn't been resolved and won't get resolved. That flaw isn't completely analyzed and won't be in the future, so the given answers, though all might have helped, weren't the solution to the specific problem. I can't answer my own question as the problem hasn't been solved and won't be solved. How can I close that question (to have that question not killing my acceptance rate)?
You can answer your own question to state what you have discovered via your research. If the question is unsolvable, the answer is that it is unsolvable. Post the appropriate documentation that has led you to this conclusion.
Forget your accept rate. It's less important than finding the right solution. If the right solution never arrives despite other people's best intentions and your own followup, then it simply never arrives. Do not feel obligated to accept an imperfect or incorrect answer just because somebody nags you over some metric.