I've been trying to understand the et'Ada and all the different groups that they splintered off into but there is a lot that confuses me.

My understanding is that Anu and Padomay are the original gods and they together create all the et'Ada. Then the et'Ada get together to create Mundus and those who decide not to, become the daedra. The et'Ada who create Mundus are losing their power and some are vanishing completely, at this point Magnus leaves and the et'Ada who follow him are the Magna-Ge. The et'Ada who are left become the Aedra and some become the Ehlnofey and Hist?

Can someone please tell the creation story in a way that defines who the aedra, the daedra, the magna-Ge, the Hist, and the Ehlnofey are? As well as how many of them are et'Ada. Does Lorkhan fit into any categories?

Also are the eight-divines/aedra also the earth bones or are the earth bones Ehlnofey that sacrificed themselves? And was it the divines or the Ehlnofey that created the Adamantine tower?

I'd also ask about Sithis but I don't even no where to start...

You're sort of on the right track.

The Daedra were dudes who were already chilling before the creation of the Mundus. There are some theories that they are Aedra from a previous Kalpa.

The et'Ada weren't just the main Nine spirits you come to associate with the earthbones. Think of the earthbones as many different et'Ada or lesser spirits who sacrificed themselves in order to become what they are now i.e. rocks, wind, water, air, gravity, etc.

The Ehlnofey were lesser spirits who decided to remain on Mundus and/or Nirn, and become mortals.

The Hist are something completely different from the rest of creation, they have no connection to any of the et'Ada or Daedra for that matter. I would explain more, but I feel wouldn't be able to give you a solid answer, so I would ask some one else.

The Aedra were the remaining et'Ada who were the original ones that Lorkhan "tricked" into creating the Mundus. The Adamantine Tower was constructed by the Aedra in the Dawn Era after Convention which marked the beginning of the Merethic Era.

I'll probably be corrected by some people, but that's ok. That's what we're here for, to help each other with the Lore.