For 3rd board wipe, I would probably go to either Living Death or Chandra's Ignition - whichever worked for the deck. I also quite like Massacre Girl and Massacre Wurm.
I would consider adding Pir's Whim to your template for decks that include black. The downside is that you don't necessarily get to remove the specific threat you want (as the opponent can sacrifice something else instead), but being able to knock out three things plus search up Cabal Coffers is pretty nuts!
It depends on the commander, but in pretty much all black decks I consider stinging study. Currently running it my ziatora deck, and drawing 6 for 5 mana and 6 life at instant speed is sweet.
I capitalize on Jund's creature removal; Grim Feast for life gain and Deathreap as a draw engine. Frontier Siege for ramp also works. Dire-Strain Rampage is underrated imho; very versatile.
Something that you didnt mention about three visits and natures lore that is DEFINITELY worth mentioning is the fact that if you arent grabbing your triome or something that has to enter tapped, if you satisfy the condition to have it enter untapped it can still be an untapped land. Searching up a shock? No problem, pay the two life, boom: untapped shockland. 2 mana ramp spells that can get you untapped lands are a great way to speed you up without having to invest large sums of money.
I really like Black Sun's Zenith because it also gets around indestructible and even if I can't take the creature out, it's still has a bunch of -1/-1 counters on it. Also, Maelstrom Pulse is a favorite removal spell for me. It is only sorcery speed, but it hits almost everything and it can completely dissolve certain token decks.
3rd boardwipe in Jund? I usually lok to Massacre Girl. Especially if you're in a sacrifice theme, you can generally control it pretty well and it gets around indestructible.
Nightmare Unmaking is top notch, for sure. I also find Structural Assault to be a load of fun in this age of treasures. Remember, Structural Assault only cares about the number of artifacts that hit the graveyard this turn, so sacrificing in response doesn't dodge the damage.
I generally love your content but not a fan of this serie. I think focusing on staples tends to make all the decks look like the same. I enjoy a lot more content about commander deck tech or underplayed cards