Using custom webhook with a specific device (instead of all devices)?

I created a custom webhook to send uplink message data from my devices to an external HTTP endpoint. However, I found that TTN will eventually start getting errors with sending this data through the webhook because the Google APIs start throttling if there are too many requests.

I hit this issue because the custom webhook integration by default sends messages from ALL devices on the application. Is there a way to only use a webhook integration with a SPECIFIC device in my list of devices?

If not, would it be best to create a completely new application with just that one device (would it cause issues to have the same device in multiple applications)?

A webhook will always be called for all uplinks/joins/whatever_you_selected_by_ticking_the_boxes for all devices in an application. If you only need it for certain devices you will need to create a new application and ‘move’ the devices to that new application.
‘Move’ because a device can only be in one application, not in multiple.

As far as I know the only way to move a device would be to delete it in the old application and add it in the new one.

No,

Yes

You can’t - it has to be in one or the other.

Regardless, how many is “too many requests”?