Mr and Mrs Miller,
My condolences on your loss.
Are you in touch with the OVV? There should be a Dutch 'Expert' appointed to the Portuguese investiugation, according to ICAO Annex 13 Chapter 5.
He should be given access to investigative material, and may be able to influence the nature of the investigation.
You might also consider getting in touch directly with Mr Lourenco.
There are independent accident investigators who work freelance, but I think your first strategy should be to understand the official Annex 13 investigation, and exert influence as you see fit to ensre it is conducted properly.
I'll look at the report again later and try to offer some insight.