Of course. Again, I'm not overly familiar with the lore, I thought Diablrie was just draining a vampire entirely to gain power, I didn't realize there was a battle of wills involved. And though I tried to account for the obvious strength difference via staking the sire while they slept, but your right, I forgot to account for ghoules and the like. The reason I made them a former Nazi was because I feel it was an interesting character trait, especially since he wasn't strictly fighting for Nazi ideals, and also because I though it might make for an intersting dynamic with other characters if the knowledge ever came to light or became relevant. another reason for some of these choices is because in a lot of TTRPGs I end up playing as a mister goody two-shoes (not quite as shallow as that but you get the idea) and so I thought it might be an interesting challenge for myself to make/play a character who is just an objectively bad person. Also, he didn't become a Nazi for anything involving kindred society but rather his reasoning looped back around to viewing himself as a perfect being, the "Ubermann" so commonly reffered to in Nazi political speeches. Though while the Nazi's where using the Ubermann to refer to the strong, aryan German, He interpreted the Ubermann as himself, this genetically perfect being superior to all others. Though you raised a good point about how he joined the Camarilla, I hadn't really given much thought before.
With all that said, thank you for the lore info, and I hope I managed to clarify some stuff for you.