I assume you already know about DecSync CC? You can point it at a DecSync folder and integrate the calendars from it into your system. DAVx5 shouldn't be needed in this setup.
For what it's worth, I used to run this Radicale+DecSync setup and switched away from DecSync to DAVx5 because it was easier to manage - DecSync is not native to Radicale. You need to have your Android hit your Radicale server with DAVx5 directly, and DAVx5 will cache the data if you move away from your network.