I am not claiming that conscious awareness and free will are proof that we have a spiritual soul.
That is your hypothesis though, is it not? If so, then you haven't provided a means of defining your terms or described a method for testing your claim, so this idea of yours really is just a fallacious 'God of the Gaps' assertion contrived to provide a personal narrative into which your 'God' can be inserted.
But the fact that these attributes currently have no material definition does open up the possibility of a spiritual soul which can perceive our brain content and interact to induce free thoughts and actions.
A
non sequitur, since it seems reasonable to consider consciousness is an aspect of our biology, alongside our other mental faculties, then it must have a biological explanation and that we currently don't know the precise details doesn't mean they aren't knowable at some point, but this knowledge gap isn't sufficient justification for you to make your claim of a 'spiritual soul' being a 'possibility' without providing a basis for your claim since if you can't, and the burden of proof is yours, this is an argument from ignorance and personal incredulity.
I could just as easily claim that we are conscious because in pre-human times an alien race left a special machine buried deep in the planet that emits 'consciousness waves' and they then altered the DNA of proto-human species so that as homo sapiens evolved we alone of all the species on Earth could detect these waves: if I did you'd rightly expect me to have a method to define and then demonstrate the existence of these consciousness waves as a starter for 10 - and if I couldn't even do that, but I still claimed they existed, then you'd be correct to just dismiss my idea as being nothing more that fallacious fantasy: as far as I can see, Alan, your 'soul' claim is on a par with my deliberately ridiculous 'consciousness waves' example.
In addition we do know that all our mental capacities and sensory responses (even the autonomic ones we aren't consciously aware of) are exclusively biological, which is why scientists studying consciousness are using methods focused on our biology and not on theology.
And it would confirm what most humans have come to believe in over the last few thousand years.
Possibly, but only to the extent of confirming what people
believed, which isn't the same thing as saying what they believed is true in reality, and especially so when these beliefs are grounded in the religious/cultural superstitions of antiquity that were limited by the available knowledge of these times - you're stuck in fallacies, again!