Do the new bone materials like Dragon bone also give stat buffs, or just the ommels? Are they even edible?
It's just the ommel bone/tooth, because they are ommel materials.
Every material is theoretically edible, the creature just needs the correct flags to be able to digest a given material type. SPOILER ALERT. Click here to see text.
See ConsumeFlags in Script/char.dat
Try polymorphing into an imp and see what you can eat.
Can you eat bone materials when polymorphed into a werewolf?
Actually no, that's a bug! Otherwise, canines, bears and necromancers can eat bone.
And petrified dragon bone is classified as a mineral, so bone-eating will not help you there.