Ethernet is always the best option to extend wifi. Brick and concrete absorb massive amount of wifi signal. There is really no way to solve this issue directly. Even if you were to say increase the power above legal levels the amount of signal the brick absorbs will also increase.
Running a wire though the wall tends to be the only good solution.
You want to run device you call a router as AP. Most have a option but any router can be made to run as a AP. You want to avoid the problems of having multiple networks in your house when you run mulitple routers. When you run as a AP it pretty much functions as a wifi radio connected via ethernet without all the extra router/nat function.
You need to protect the router you...