Romnipotent said:
Does Farugon keep the dwarven racial weapons?
Does Farugon get the elven racial weapons?
Assuming Farugon had fully progressed as a Dwarven defender and was now also another PrC or some other class would he keep all the DD levels and benefits?
Would you even consider letting this happen?
I agree that he should keep everything he has learned, while everything he was "born with" should be adjusted to match the new race. If this leads to being better or worse than a normal character (DM's call), I might have ruled in/out some of the less obvious feature, such as the ST bonuses vs spells.
Probably I'd go this way in this case:
+2 Dexterity, -2 Constitution (as Elf)
Medium size, speed 30 (as Elf)
Immunity to sleep (as Elf)
+2 vs Enchantment (as Elf) -> debatable, I'd say it's a mental innate ability
+2 Listen, Spot, Search & autosearch for secret doors (as Elf)
Weapon Familiarity (as Dwarf)
+1 attack vs Goblinoids & Orcs (as Dwarf)
+4 dodge vs Giant (as Dwarf)
Various languages (as Dwarf)
Favored class Fighter (as Dwarf)
Now what's blurred IMO is Stonecunning and the +2 Appraise/Craft. I am not sure if I would treat this as something learned from Dwarven culture or otherwise coming from a sort of innate link with everything stoney and earthy

. Also I might rule that he keeps only part of stonecunning, perhaps the sense of depth is not learned but innate? Maybe I'd be generous and consider everything cultural, so he'd keep all of them.
Finally about the Dwarven Defender, I'd let him keep all the levels and continue advancing with no problems. It depends on what's your campaign issues with this PrCl: if you play that you need training from the DD masters to advance, then he's probably stuck to what he got so far. But to me the features seem quite straightforward, so I could imagine him keep training in this way of fighting. That's mostly a campaign issue IMHO.