Regarding nib-swapping, I just tried this on my new Prometheus last night. The nib unit does NOT screw out, but you CAN pull the nib and feed straight out and swap if you wish. Perhaps mine just needs some extra "encouragement" to screw out, but it may indeed be glued in there. I wasn't going to force it, lest I break something.
The nib is Jowo alright, but the feed is different from all other Jowo nib units I have. I have no clue what's going on. Perhaps the "Prometheus" is, aptly, a "Frankenpen."
I have three (3) of these Prometheus's in different colors. Each one of the nibs
screwed out as I replaced each of them with nibs from other pens. You are right,
it just may take a little coaxing but I sincerely doubt it is glued in.