The White Court isn't so easy to figure out, some aspects of it seem to play for the team, it is possible that the Hunger Demon itself is part of the Enemy, but with varying degrees of success.. I think it depends on the family, Thomas must feed, but perhaps because of his mother and brother doesn't act like someone Nemesis infected. Lara on the other hand is harder to figure out, she works strictly for self interest and plays both sides I think.
He was protected long before blood rites. Which is why a wizard of Margaret's calibre went for a crippling blow with her death curse instead of a death blow.The possessed by an outsider bit has merit though.
Maybe not.... Jim did say that if he had been killed he would have been replaced and the White Court would have continued it's growth but she sandbagged them for 30 years. It may have been her intention to cripple not just him but the entire White Court. My guess is her way of doing it was through her son Thomas who shares his father's blood, and inherited his demon from him. She used that link to get to Raith's demon and put a muzzle on it. It may have been after his demon was crippled, and his paranoia grew (when they cannot feed this happens) that he reached out and got the magical protection.
I agree that her hope was that Thomas could help to check mate Papa Raith, but I don't think he inherited the same Hunger Demon. Simply because Thomas can feed and get nourishment from feeding where as his father cannot.
Thomas's demon came from somewhere. I figured his father's demon provided some sort of material just like any parent would provide to create a life. Maggie could have used that to go after Raith. Either that or Thomas's blood or maybe she actually had stolen some sort of physical material from Raith herself.