It's not an argument for the existence of God, but it's an argument for a belief in God's existence being one rational position amongst others.

I totally fail to see how taking something on as an axiom makes it rational. What belief would fail this test?

If I were just searching for a safe place, I think my religious history would have been rather different - it's not as if I haven't been willing to change my religious beliefs in the past, for instance,

But did you do so as a result of reasonable arguments?

and I did identify as an atheist for a large chunk of my teenage years.

What changed your mind? Serious question, not snark.

I probably also wouldn't engage with atheists on the subject as much as I do.
It's hard to see it as a demonstration of a commitment to rationality when the result of that engagement is that your views are placed out of the reach of reason.

As far as I can tell, theism really just is the only way I can make satisfactory sense of the world as it appears to me.

But it isn't, because you successfully eg made cups of tea and such when you were an atheist; you didn't succumb to total inability to think due to universal skepticism. If you have the power to reason about ordinary things, then we can start to talk about less prosaic things starting from there.