Crikey! Whatever dear old dad said must've been pretty fucking hateful to make his wife commit suicide and his son run away from home. If said son is Samuel, no bloody wonder he took out a contract on his own father! I'd wager he'd also resent Enoch for having it better than he did.
I'll say. Outside of the one party scene in DMFA (which was never really equated to alcohol) I hadn't considered the ramifications of things like drinking on cubi. On magic users sure, give a wizard a few too many shots and they're bound to use magic recklessly. But yeah, I imagine it was probably some relationship twisting thing, like having replaced a previous lover or having only been in it for selfish reasons.