I think it's safe to say that whatever existed before our Universe, was certainly in a different form than it is now. Time and space came into being with the big bang, as well as the rules that govern physics, so to say "immaterial" could simply mean "existing outside of our immediate material universe". We can really only understand material as it relates to the rules of our Universe. At least for the time being, we are stuck with observing the limits of our known dimensions.
I also don't think the possibility of better fine-tuning negates the fact that we currently have a fine-tuning which works well enough for us to rely on science, reason, and rationality. So the fine-tuning is still valid as far as I'm concerned. Just because you can make a faster car doesn't mean the slower car is invalid. It's just not preferable (to you).
Romans 1:20 essentially highlights the argument I presented earlier. When you see something created, you assume a creator. It's normal and natural. We apply this logic to everything EXCEPT nature itself, and the universe. The "invisible qualities" the verse refers to is the power to create the universe and everything in it.
This is all assuming the physical universe is all that exists/matters. If that were the case, yes you would be correct. But in light of a spiritual or transcendent reality, it would make sense to live in a world that leaves you desiring more. If we lived in a perfect ideal world, we wouldn't want to leave it.
But as far as the notion of "why would God guide evolution through such a slow process/take billions of years to create the universe?" Well... I'm certainly not going to pretend to understand his intent, but I appreciate that we have something to study and discover when it comes to our origins. If it happened in the blink of an eye and we had no concept of how, I think life would be quite boring, especially for scientists. I also think it's easy for us to label the system as "inefficient" or "slow", but to a potential infinite being that exists outside of time and isn't affected by time, it would presumably make no difference to him. Plus again, maybe a more efficient way would prove boring to discover, if we were able to figure it all out so easily. Or maybe I just think it's a bit arrogant for us to assume we can do a better job creating a universe that allows for life lol
Here's how I see that as a creationist: I believe the fine-tuning was planned by God to allow for evolution. The only caveat I would throw in is that I believe more specifically in guided evolution, and not random mutation. I think you've mentioned Occum's razor before, and I would apply that specifically to the chances of us even existing. The simplest explanation is design. The other explanation is an infinite number of universes, which only raises more questions. And of course we haven't even invoked Alien spore theory, which raises even more questions.
I completely understand how scientifically minded people can't accept the concept of God, and that's simply because it lies beyond the scope of the observable universe. Essentially it requires faith and that's generally too much of a leap for some people, but for me science is limited in what questions it can answer. It deals with the "how" but not the "why". I'm sure for some folks that's not a big deal but all I can say is that I've been through a lot of sh*t in my life that caused me to ask very deep questions to which science alone couldn't answer.
You may think that one does not need meaning or purpose, but it's by far one of the biggest correlations with happiness. Tell that to a person suffering from severe depression and see how that goes. I'm sorry but it's not wishful thinking. Its reality as far as I'm concerned. Would you tell your child there is no meaning in life, and that your relationship and love for them means nothing? Of course you wouldn't.
And to some degree, yes, you're right. I refuse to believe that this world has no ultimate meaning or purpose, and that its all random. I can't live my life like that. And if I'm wrong, then according to science, I'm pre-wired to think that way anyway lol