I found quite a bit of information, and didn't find it lacking at all. I DM'd a fey'ri campaign for a few levels.
You already seem to know that the Silver Marches gives you details on Elven Port, even a picture of its leader (fey'ri Ftr2/Wiz9) "welcoming" visitors, and claims the daemonfey are located in the ruins of Lothen of the Silver Spires; it refers also to Lords of Darkness.
Personally, I think that's quite enough.
Lords of Darkness has a few more details to add - such as that there are 32 fey'ri amongst the daemonfey, that their leader is Sarya (sun elf half-fiend So17), and rules along hew newphew Xalth (barbarian), and that she killed her son Ryvvik. It also has a picture of Sarya (not a good one), and an example daemonfey bolthole. All in all - about 4 pages worth of material, but much of it repepeitve.
I don't own Races of Faerun, and can't remember what it says, but it seems you have it. I do remember it having another, more balanced, version of the race as characters.
If you want, you can look at my
campaign web site; the first chapter of the log might give you some ideas on my view of their society. I was going to write more sizable treaties on their role in Hellgate Keep, and other tidbits - but I didn't get around to it and the campaign ended.
The real historical details, IIRCS, were presented in Hellgate Keep - which you can get cheaply through RPGNow. Though you'd have to sift through a lot to get them, and as I recall I wasn't overly impressed with my findings.
I hope that helps,
Yair