God's existence--A different approach

But how do you know that the reality is a created construct?
Why can we not postulate that the framework has always been there, and it's only the contents - the matter and energy - that necessarily had a cause?

Because it exists. Sheer randomness can not create the sort of rigid and strictly enforced structure that is our reality.

But let's assume the universe was in fact created. Something triggered the Big Bang. Something that is clearly outside the rules. What reason have we to believe that that something is omnipotent, omniscient, and omnibenevolent? What indication is there that it's even sentient?

Cause and effect, again, too structured to be chance. An intelligence had to create such a framework. It's improbable that our entire reality is the single instance, even within itself, of such complexity just appearing naturally.

As creator of such a complex work it's not improbable or impossible that they have absolute and complete power over it, but it's also equally probable that once created and set in motion it's fully self contained and they have limited to no ability to interact with the contents (such as us). It's also entirely possible we're an unintended side effect spun off from the true purpose of their creation. The bizarre idea that we matter and that our creator is somehow "good" or "favors" us is too egocentric for me. That omnibenevolent clause is just absurd since for it to be true there would have to be least one other force or entity responsible for everything that wasn't good and then you're not just trying to come to terms with whether or not we have a creator, but whether or not we have a dichotomy.

God and science are not mutually exclusive, nor should "God did it" be the end all answer; The end all question should always be "how did God do that".