The Principle of Contingent Causation: The Impossibility of Infinite Regress.

[polymath257]

Belacqua

Implicit in your argument is that a "being" of some sort or other caused anything.

No, that's not what the argument says. 

It sounds as if you are anthropomorphizing the First Cause by calling it a being, with the indefinite article. The First Cause is not a being, it is being. 

Not according to the OP. furthermore, 'existence' is a property, not a thing.

Too many people think of the First Cause like a big guy who decides to pull the levers to start things going. It's nothing like that. It is the thing which must be the case in order for anything else to be the case. There must be being in order for any contingent thing to be. There can be nothing essentially prior to being, because that thing would require being to be, and that's a paradox. 

OK, so the universe of spacetime 'simply exists'. It is being itself.

The word "cause," in these arguments, is not the same as the modern English word. It is the translation of the Greek αἰτία. The αἰτία of X includes all the things which must be the case in order for X to be the case. 

Which assumes some sort of physical laws to produce the dependence.