I would absolutely not go the wireless route, that will expose you to all sorts of latency issues.
Now I'm going to tell you what your fundamental error was. You placed an AV cable in an inaccessible location without placing it in conduit. Any unexposed AV cable of any type, including speaker wire, that you can not get at, should always be placed in conduit. There are NO exceptions to this rule. If you had placed that cable in conduit, you would not be in the pickle you are in now.