You wrote, ” In some of your writings you say that we can’t really say much about what nibbana is like, because it is so far beyond any worldly experience. And in one place you even say that one arrives at nibbana at the 8th jhana.”
That is not true. Please provide the link to my post and quote from it.
One attains Nibbana when all defilements (lobha, dosa, moha) are removed from one’s mind. That is Arahanthood.
– But Nibbana becomes complete when that Arahant dies and is not reborn in any of the 31 realms in this world. That is “Parinibbana” or “full Nibbana” for an Arahant.