Pulling fiber cable between the 2 houses will provide a much more stable connection
You just have to find a way to route & hide the fiber cable properly. Preferably inside the longkang protected with a PVC pipe

You'll need 2 units of Fiber to Ethernet converter, 1 for each house like this:



You also need SC to SC fiber cable to connect the 2 Fiber to Ethernet converter like the image below



Then install another router at the second house so they can have their own Wi-Fi