There's not a lot of recurring drawing in W/B, and even less if you're trying to stick to Modern or later. The first ones that come to mind are Phyrexian Arena and Land Tax, and I'm not sure that either of those fit what you're looking for. Your Night's Whispers thoughts are a good choice, and I personally didn't have any issues with Sign in Blood, but meh, to each their own.
There's also the other one-use options of cards like Street Wraith and Twisted Abomination, which can provide backup "brute" plans if you can't get your combo sorted.
If there's enough spirit cards in the deck (not that I recognized, but you'd know), you could always use Angel of Flight Alabaster to mimic a draw by recurring a dead spirit every turn.
These ideas brought to you courtesy my own favorite B/W decks,
Tombstone Teysa and
B/W Spirits.