How to change outbound and routing configuration to use a middle server as main server and use other servers as endpoints to distribute traffic by ip/domain strategy?

[caribbeansyrup]

Here's the scenario:
we have 3 servers, server A, server B and, server C. End users will connect to middle server which is server A (the main panel is on this server) and based on some routing configurations, they will use sever B or server C. for example for streaming and finance purposes.
I tried this but doesn't worked:
I defined a new outbound tag in 06_outbounds.json and set a wireguard configuration for connect to server B

{
      "tag": "to_server_b",
      "protocol": "wireguard",
      "settings": {
        "uuid": "***********",
        "udp": 1,
        "keepalive": "",
        "dns": "",
        "type": "WireGuard",
        "title": "server B WireGuard",
        "host": "server B address",
        "password": "***",
        "data": "",
        "privateKey": "***",
        "ip": "10.0.0.1",
        "publicKey": "****",
        "reserved": "0,0,0",
        "mtu": "",
        "port": "***"
      }
    },

Then add a routing configuration to 03_routing.json like below:

{
          "type": "field",
          "outboundTag": "to_server_b",
          "domain": [
            "domain:sample.com"
          ],
        },

Then I tried to change the "freedom" outboundtag to redirect all other traffic to "server C" but I couldn't.
So, There's two main questions:

1. How can I do this properly
2. By every "apply config" action in panel, it seems this file will updated, I should update files (03_routing.json and 06_outbonds.json), manually and restart xray service. How can I prevent this

Regards,