Hub load is severe - Maker API? Bad Hub?

A few points:

  1. Hubitat has evolved quite a bit over the past couple of years. You should probably bring yourself up to date on the capabilities. They've really tried to make automations better and easier. About the only thing Home Assistant does better out of the box is dashboards + a few IP integrations (IMO).
  2. The Hubitat beta HomeKit integration is truly beta. Lots of issues in the first couple of rounds. If you are easily frustrated wait for a while.
  3. It looks like you are using
    [RELEASE] Homebridge Hubitat v2.0
    That's the one that seems to be actively maintained now, which is good. Make sure the device you are running Homebridge on is totally up to date
  4. If you are only using Hubitat to connect 'Z' devices to Home Assistant you may find it easier to move them to Home Assistant directly. Their Zigbee and Z-Wave integrations have improved a lot in the recent past.