I just finished watching Record of Lodoss War again and got me thinkin about it as well. While I think most of the standard D&D stuff can fit into a Lodoss setting without much trouble, some of the things in it just seem it would too awkward to handle without house rules or something; like how just about anyone with a magic item or magic skills can instantly pop up a barrier for a defense.
You might want to look around the
Yahoo group , but it seems to have been forgotten by the others. While no posts anyone, some of the previous threads might be useful and there are some links to other 3e Lodoss sites.
There is also a Fuzion conversion of Lodoss asa PDF somewhere, but the site that origianlly hosted it decided to take it down cause of possible law-suits or something. If I can find it, I will try to put a link on my site. It has very good information on just about everything. I believe it was converted from the original Japanese game itself.
As for your questions:
1 & 8 seem to be a DM call to me.
2. The core magic system can be used as is, but I see it more as a point-based system like psionics. I know I mgiht be blasted for that, but in the series never do you see Slayn or any other magic-user use anything but incantations and simple gestures when castng spells, no material components are ever seen.
3. Humans and dwarves can be used as is. From what I've heard, there are 3 types of elves; normal, high, and dark. The normal and dark elves would be as the core elf, but the dark elves would have some penalty when dealing with non-Marmo people. The high elves would be interesting. They say a high elf is immortal so... I personally would jus have them as standard elves as well, but with an immortal lifespan.
There is an equivelant to a halfling called a Grassrunner, but I have no more information on it. As for any others, I'm not sure.
4. I'd say less common when compared to a typical D&D setting. If I recall correctly, you never once did see any sort of 'mundane' magic item, only items of true power or one with a history behind it.
5. From the 3.5 SRD; I'd say Archmage, Blackguard, Hierophant, and Loremaster. The rest either seem to not fit or there hasn't been any clear evidence to has a clear say on the matter.
6. Feats and the weapons used. While watching it again, I'd say Parn uses a longsword two-handed while someone like Orson would be using a greatsword. But really? Is there any difference between warriors? They all wear armor, swing swords, and are good in a fight.
7. These are some suggestions from the top of my head so...
* I would make the Paladin a, or have a paladin-esque, PrC and the Ranger as having no spells. The shaman class from OA might be a good class for someone like Deedlit who calls on elemental spirits for spells.
* Maybe all arcane casters are sorcerers and wizards (as a class) isn't available.
* The Hyuri spirit (berserker spirit) would be a template that would have uncontrolable barbarian rages triggered by some situtation (and making the barbarian class obsolete).
* The five ancient dragons (Narse, Myce, etc) would be statted as from the Epic Handbook.
* I'd drop the Adept NPC class; either your a sorcerer or a cleric.
* Lodoss kobolds are just D&D gnolls.
* I remember once someone said that the green worm at the end episode which Slayn faced reminded them of a mix between a roper and a purple worm. maybe someone could mix the two ad stat it out here?
PS. You might want to try watching the Legends of te Heroic Knight which I think is the tv series which is based after the original series. And there is also the Legend of Crystania, but I really don't think it has the same feel as teh original. Of course there is also the manga (comics) as well.