JSON api consumption pointers needed

I have the following in my configuration.yaml, in an attempt to report the remaining mass of pellets in my pellet boiler.

rest:
  - resource: https://stokercloud.dk/dev/getjsondriftdata.php?mac=XXXXXXXXXX
    scan_interval: 60
    sensor:
      - name: Hopper Pellets Remaining
        value_template: "{{ value_json.505 }}"
        json_attributes: "505"

This is to consume the following JSON, which reports the mass of pellets remaining in the hopper under id 505:

{
  "501": "22.8 °C flow",
  "502": "0 % Power",
  "503": "21 °C Shaft",
  "504": "0 kW Power",
  "505": "813.7 kg Hopper",
  "506": "0 Lx Light",
  "507": "Stopped clock ",
  "508": "07-29-2024 13:13:46",
  "521": "0 °C Return",
  "522": "0 liter/hour Flow",
  "524": "0 °C External temperature",
  "525": "48 °C Temperature DHW",
  "526": "16.2 % Actual oxygen",
  "527": "20.9 % Target oxygen",
  "528": "1450 Gram auger/6 min",
  "530": "0 kg Today",
  "531": "0.000 kg/m2 Today",
  "532": "0 °C Smoke temp.",
  "533": "75 °C Target boiler temp.",
  "534": "65 °C Target DHW temp.",
  "542": " ",
  "584": "REDACTED",
  "585": "41 % humidity",
  "586": "1021 hPa pressure",
  "587": "4.1 m/s wind speed",
  "588": "http://openweathermap.org/img/w/01d.png ",
  "589": "26 °C air temperature",
  "591": "130 null",
  "592": "0.0 °C T5",
  "alarm": "0"
}

This almost works as I would like. It creates an entity, with an attribute of “813.7 kg Hopper”. However, I would like to make two improvements:

  1. I want this to be reported solely as a number. I’ve tried the following but it is not the answer:
        value_template: "{{ value_json.505[0].replace(' kg Hopper','')  }}"
  1. I want this to be reported as the status of the sensor. This may be incorrectly phrased as a desire, but I want to be able to view this as the primary value in a graph, create notifications/alerts on the basis of this value, and to view it in dashboards as a single number.

In addition, it may be good to consume other values from here (e.g. “alarm”), and I’m not sure how I would extend this to consume multiple values, would it simply be to append more lines such as this?

    sensor:
      - name: Boiler Alarm
        value_template: "{{ value_json.alarm }}"
        json_attributes: "alarm"