Arguments for God's Existence from Contingency

[Whateverist]

What is wrong with saying the universe is contingent at every moment upon its prior states and we just don't know how far back those go, nor whether they extend beyond the range of what we locally call the big bang.

Your just pushing the problem back a step each time. You can't have an infinite regress, so it has to stop somewhere. For the sake of argument, "the universe" is used to hold the place of some point in the past.

But what else can one do?  The problem of deducing what makes possible what we do know intractably requires making assumptions about what we don't know.  Your hypothesis is that over and beyond the natural world there is a supernatural world which somehow gave rise to the known natural world.  My hypothesis is that there is a wider natural context which for reasons of our own limitations we cannot know which gave rise to the known natural world.  We are both speculating regarding that about which we cannot know.  The difference is you think you can deduce your way to knowledge of the unknown based on what?  Your assumption that the natural world owes us an adequate explanation?  Not sure where you get that sense of entitlement.  I prefer to let my hypothesis remain what it is, meaning the explanation remains incomplete.  The infinite regress is only a problem for those wishing to wring certainty from our hypothesizing endeavor.