The First Cause is X.
You cannot establish a
"First Cause". The assumption you make here is that time is linear i.e. a beginning and an end. Where is your support for this?
X does not exist in space and time.
Which "space" and which "time"? You are using arbitrary definitions.
X has always existed.
This is an assertion...if something/someone exists outside of space and time, how does that allow you to use this definition of existence?
That's the only qualities we can assign to X.
You can't even apply this further.
Not that I want to lend credence, but how does this prevent this entire event from being caused by a leprechaun...I mean call it whatever you want. As Mike says you have disproven nothing.