Ok, the concept is very nice (and the array of powers too), but there's a small problem with the races you picked. That is because both angels and demons aren't monsters, they are spiritual beings, good spirits and evil spirits, respectively; They can be interacted with using magic, like being summoned or communicated with, but they wouldn't be able to produce offspring. I would presume that this book series you mentioned have a more materialistic view of these creatures, but in the setting of our game, fairies, ghosts, angels and demons (I would presume djinns too, but they don't appear in the series) are a different class of beings, they don't even dwell in this world (unless invoked by magic).
Just to clarify, the Succubus character which appears in the main series isn't actually a demon, its race just being mistakenly associated with demons by humans. Of course, your character could be a monster race with aspects that resembles both angels and demons in their popular portrayal, but actually aren't (like the succubus).
Now, about your character's appearance and powers:
- Technically, any monster can learn magic, though some are more talented than others.
- The canon races that are shown to be most talented with such "holy magic", or "dark arts", are the Yasha (which have an entry in the Monster Encyclopedia already) and the Kishin, which are a class of powerful oni (they don't have an standard appearance, the one from the series being shown as a large humanoid with horns).
- The sword wouldn't need to be related with your race, it being simply an item.
- The appearance you described could be achieved by picking any monster from folklore or fiction that has those traits, but I doubt you'll find any like that, as they're completely contradictory symbolisms, but you could adapt anything that isn't yet pre-estabilished by the lore.
- About being a hybrid, children of monsters from two different races would normally inherit the race of the more powerful parent (having a stronger blood), but some odd ones could inherit the race of the other; besides that, it would be reasonable for then to inherit some minor aspects of the 'recessive' race, in both appearance and abilities. The one exception would be chimeras, which are composed of a mismatch of different monster and animal parts.
That said, I always prefer to give players total freedom for their characters, but in this particular case, I don't think it would be thematically appropriate.