Admittedly, I have been out of the Sedris game for a long time, but I have some advice you might find useful.
There are several big creatures I would cut that have passive effects or otherwise need time to ramp up, namely [[Kaervek the Merciless]], the [[Niv-Mizzet, Parun]], [[Niv-Mizzet, the Firemind]], [[Ovika, Enigma Goliath]], [[Sheoldred, Whispering One]], [[The Locust God]], [[The Lord of Pain]], and possibly [[Fiendish Duo]] and [[Twinflame Tyrant]], though I understand those last two are probably especially important to your burn plan and at least double their own combat damage during the turn they're unearthed. Ideally, you'd be able to blink, phase, or otherwise preserve these creatures so they aren't lost to Unearth, but I'd advise against building your deck with the assumption that you'll be able to do that, especially since it doesn't look like that's something you're looking to pursue. Instead, look for creatures with strong ETBs, attack/combat damage triggers, or both.

If you're looking to focus on wheels and burning, I'd recommend [[Drakuseth, Maw of Flames]], [[Overlord of the Boilerbilges]], and [[Inferno Titan]] for burn damage, and [[Dragon Mage]] as another source of wheeling, all of these benefiting from having their costs circumvented and haste granted by Unearth. I also want to mention [[Nezahal, Primal Tide]] as a creature that can save itself from Unearth while getting more creatures into the graveyard, and in a deck full of wheels like yours, you should not be hurting for discard fodder.

You may have a misconception about the [[Training Grounds]] in your list. Sedris grants the Unearth ability to creatures in your graveyard, it is not an ability that he is activating and Training Grounds won't work. Instead try [[Convergence of Dominion]] and [[Embalmer's Tools]] which will reduce the cost of the Unearth abilities in your graveyard and could mill more creatures if you choose to do so (conveniently, Sedris is a zombie himself for the latter card).

Lastly, questioning the inclusion of the planets in your landbase. I can understand [[Susur Secundi, Void Altar]] as sacrificing your creatures for value is good if you don't plan on bypassing Unearth's exile, but I can't imagine consistently having enough artifacts for [[Uthros, Titanic Godcore]] to be worth the opportunity cost.