Specifically, I'd like to add thermalfoundation:ore with a meta data value of 3 to the config in order to disable lead. Is this possible?

Perhaps this will help?

As you probably could have guessed from the link above, you specify those by using their block state properties. To disable TF lead, create a custom ore config JSON with something like this in it, untested:

{
  "state": {
    "name": "thermalfoundation:ore",
    "properties": {
      "type": "lead"
    }
  },
  "enabled": false
}