Thank you. I would try to focus on draw/drain and protecting and accelerating the combos. Potential cuts: Angel of suffering, grave pact, dictate as they protect only if you do something. The same for grim haruspex and morbid Opportunist. Praetors grasp has no synergy. Leaden myr is too slow without haste. Oversold Cemetery is conditionally slow. Doomed Necromancer and Phyrexian Reclamation could be ok as you tutor things into the graveyard, although I would go for Witch's Cottage and Volrath's Stronghold.

Potential inclusions could be Imp's Mischief for protection, cheap targeted removal and mana rocks like Mana Vault, Grim Monolith, Mana Crypt.

I look forward to seeing two new decklists ;) I think for now I am out of ideas but would be interesting to see how this turns out. The deck would be way out if my budget and for my playgroup Sheoldred is not a suitable commander but I really like her in the 99 for my Braids Arisen Nightmare deck. Hope this works and I really like the deck!

With Dauthi voidwalker and oppression there is also a small discard subtheme. This could work with the apocalypse although I do not like discarding my own cards if I am not in reanimate theme. I would cut scourge of nel toth because it is 6/6 flying for a high cost whichever way. And I would incl Cabal Coffers and stronghold as additional lands. Regarding good lands may I point out Volrath's Stronghold and Lake of the Dead.

I think it may be helpful to decide which strategy you want to follow. With your current commander the recursion and Reanimation effects do not have a synergy. If you want to be more competitive maybe decide which sheoldred will helm your deck. The acopalypse is for draw/life drain. The whispering for Reanimation. If you stick with you current commander you could cut cards without synergy with her. However, a subtheme is nice if not competitive and I prefer decks like that :)

Some other cards that may be of interest could be Necropotence, Archfiend of Despair, Wound Reflection, Pox.

And I agree regarding the mana base.

Memory Jar, Dark Deal work well with Sheoldred. Orcish Bowmasters adds as well. Demonic Tutor, Vampiric Tutor are more competitive. Jet Medallion for mana.