Sean Hampton's comfort toward William Bishop and refusal to believe the cross would repel vampires makes sense when you take into account he's already friends with Old Bridget and the Skal community.
Sean Hampton going crazy and murdering everyone in his district seems out of character given other Skals' behavior who aren't psychopaths. Then you realize he's infected with the blood of hate. This also explains why turning him into an Ekon will cure him; feeding him Jonathan's blood exposes him to the same immunity to the Blood of Hate that Jonathan seems to have.
Lord Redgrave only banishes you from the Ascalon Club when you defy him despite Elisabeth's claim he will try to kill you. Later, when you return to the club for William Marshal's blood, he folds like a cheap suit no matter how hostile you are. Then you note he sends Ekon assassins after you, who try to kill you. This is because Lord Redgrave is of a lesser lineage and you've already killed his chief enforcer. Redgrave is a Dirty Coward!
Lord Redgrave is only able to get away with passing himself off as William Marshall's progeny due to the fact the Great Hunt destroyed most of the ancient vampires in England. As such, no one is there to contradict his claim but Elizabeth.
Lord Redgrave's misogyny and distrust for immortal women probably comes from the fact his wife, Old Brigit, loathes him for changing then abandoning her.
Lady Elisabeth has no desire to change her daughter Charlotte because she's infected with the Blood of Hate and would create another monster. Ironically, now that she knows Reid, she could probably have him turn her. We also discover that the change is very often lethal.
The existence of the Blood of Hate explains why the vast majority of vampires created during the Spanish Flu seem to be a collection of psychopaths. The influence of the Red Queen has made them into monsters with a Horror Hunger far stronger than Jonathan's own. Regular Ekons and Skals may be good or evil but the ones created by the Disaster are Always Chaotic Evil.
Jonathan doesn't seem afflicted by the Blood of Hate, despite regularly feeding on Skals. Then again, he was sired by Myrddin himself, a vampire so powerful and ancient his species is unknown, which likely makes him immune to the effects of the Blood of Hate. That probably also explains why, even as a newly-born vampire, he's able to take apart much, much older and seemingly more powerful and experienced vampires. This would also explain why Jonathan turning Sean into an Ekon could cure him of the Blood of Hate, since he's just one step removed from Myrddin himself now.
It's show that is also possible by accident by just biting them as seen with Mary Reid without having to exchange any blood. Its inevitable that you gonna have to chomp on a few enemies to regenerate health and gain experience points - specially when playing as an Friendly Neighborhood Vampire, since this is the only you can level up. Let's hope that Jonathan makes sure any of his victims stay dead and don't rise as vampires...
Assuming that Jonathan being unable to gain experience from draining Prywen guards isn't Gameplay and Story Segregation, Mary must have drained a ton of civilians to catch up to him as quickly as she did.
West End has a sizeable population of Ekons (and two Skals right behind Jonathan's house). Jonathan's mother Emelynn has a tendency to wander off alone due to her schizophrenia. It doesn't take much to realize that she is in constant mortal danger with how much of an easy picking she is.