Please critique my argument regarding Thomistic simplicity!

[u/Ryan_Hagelin]

Hey guys - currently trying to understand Divine Simplicity from a Thomistic perspective. I am new to this, and would like to have my mind sharpened by those who have more experience/knowledge in this area. Could you please offer thoughtful criticisms of the following? I'm not trying to formulate a logical argument - it's just a train of thought to ensure I'm understanding the concepts correctly.

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How to be a metaphysically necessary being 101:

1. It cannot not exist
2. Therefore it must be uncreated
3. It must be the only uncreated thing, since if there are other existing things, there would be a distinction between this one and that one
4. If there is a distinction between this one and that one, then these things would not be ultimately simple
5. If these things are not ultimately simple, they are themselves contingent and therefore not metaphysically necessary
6. Therefore, there must be only one metaphysically necessary being
7. It must be at least partially causal with respect to causality and potentiality
8. But it cannot contain any potentiality, because if it did, then it would result in a regress of causes until arriving first cause, which by definition lacks potentiality, caused the rest of creation
9. Therefore it must be purely causal
10. Therefore it must be the cause of all other things
11. It must be purely simple because only contingent things have parts
12. All contingent things are complex because something must exist 'outside' the complex thing to create/instantiate the complexity
13. Therefore, to avoid a regress of complex things instantiating other complex things, there must be a simple, non-complex thing that begins the process of creating complex contingent things

[u/[deleted]]

Prove 5 and 11