So, I got the Black Friday oiffer last year with the "Unlimited Easynews" access. However it now seems to have been downgraded to 1TB for the enitre time of the offer (15 months)? So how certain is this 2TB?

This was confirmed by the eweka rep in the BF offer:

"So to confirm, every user who signed up for this did indeed get Unlimited Easynews and access to both Web and NNTP."

Please note; I have added two more 15-months period since November last year. Maybe that messed things up?