Ill try to answer as best as I can.
1. Fellowship npcs do not work.
2. OWNMs are what they are called, each one represents a specific BCNM, some of them are listed at
http://nasomi.com/wiki/doku.php?id=nms:open (there used to be a much better list but due to an issue, all of the forums and wiki were lost some time ago)
3. Blu works, some spells arent as good as they used to be it seems, but I have a feeling some may be better than they were that were never used in retail. You can get all the spells, but aht urghan ones are a little harder to get since all the mobs are lvl 99 so going to need a party of 75s and a good amount of effort to be able to kill them.
4. Never seen any marriages on nasomi.
5. You can get all the summons up to fenrir and diabolos.
6. Nations usually change regularly, since its a smaller population, you can actually go out with some people and make a difference if you focus on EXPing in certain areas for the week with people from your nation, seen people do that to get outposts they didnt have.