If there were only slight differences in the laws of physics, the way the universe is structured etc., then life would be impossible.
That is an inevitable truth, as we do not know the number of other universes, if any, and whether they were capable of supporting life, if any. Nor do we know about any other life in the current universe. Life may have failed to arise many trillions of times over, and it may be that the fact it has seems miraculous to us is because we are only able to observe the single successful event.
To put it another way, if you played the lottery 150 million times and won on your 150 millionth try, and only told people you played the lottery upon your successful instance, people would naturally assume your astounding luck.
Apparently if water were not the only substance lighter as a solid than as a liquid, then life would be impossible. Furthermore, the essential element of water is really versatile. If everything is a big accident, then it is really convenient that something like water exists. If everything is a big accident, did gravity have to exist? The universe would be unworkable without gravity.
Same goes for water, gravity, hydrogen, you name it. A single perfect instance or endless failed efforts, there's no way to know.
Life itself is a miracle -
A miracle is something that
cannot be explained, currently there is no way to know if that will ultimately hold true. A great many mundane things have been labelled miracles throughout history; something like an eclipse was once fantastic, without any understanding even of what it was, let alone how it worked.
is there any other example of the whole being so vastly greater than the sum of the parts? Any creature can be reduced to a small pile of chemicals plus water. How do these raw materials create something so complex?
I'd say you're using an example right now. With just two digits: 1 and 0, the breadth of human experience can be represented without limit. Extreme complexity from extreme simplicity is something we have already observed and reproduced ourselves, a more pertinent question would be whether something like computing could arise spontaneously or evolutionarily through naturally occurring 1s and 0s.
One could argue that, from humble beginnings with limited tool use, the formation of language, the discovery of numbers, through mathematics, mechanics, industry, silicon, connectivity, it's as clear an example of unlikely wonders beyond primitive imagination evolving from absolutely nothing as you could wish for.
Not the least of the complexity is consciousness. Has anyone ever analyzed consciousness, or isolated it in a test tube? This suggests that more exists than just the physical universe.
Consciousness is easily isolated. At it's simplest, it can be easily controlled with anesthetic. It can be lost entirely through severe bodily trauma, emotions can be altered with stimulants, personalities changed through surgery, specific functionality observed with brain scanning. There is no doubt that consciousness physically exists in the brain and is supported by the rest of the body. To a very limited extent some of the mechanism is known as well.
That is no conclusion that the origin of consciousness cannot be supernatural, but since you again say it's a matter of complexity I don't understand your point, or why it cannot be an extreme incidence of the complex physical.