God's existence--A different approach

Actually I still disagree with your first premise ("- everything that exists has a cause"). There is no proof of this.

Wouldn't that be the law of causality?

Plus, if we do accept it, it must apply to God himself. If we allow God to be an exception, we must also be able to allow the universe as an exception: "Everything in the Universe has a cause, but the Universe itself has always existed".

I'm not following that logic at all. If the reality is a created construct, created by an entity outside of that reality, the exception of the creator would be obvious (though as noted, it's also equally obvious that some rules governing the reality that the alleged creator lives in would apply to both that creator and to our construct) but why would the reality/universe itself have an exemption since it were created within it's own ruleset?