> There really are many more units, with the option of increasing the divisibility past eight decimal places in the future.

You are still missing the point. It is not divisibility that makes bitcoin unsuitable as a spending currency, it is the fact that its price keeps rising. Imagine if you are presented with two coins one that historically inflates and another that deflates and are asked to spend one and hold the other. Which do you pick? An inflating coin will always replace a deflating one as a medium of exchange. This is called Gresham's law.

A coin with a fixed supply will never be suitable for daily transaction because the demand for currency isn't fixed (due to economic and population growth).

Bitcoin is currently inflationary. 1,800 newly generated bitcoins (about $11,700,00) are added to the supply roughly every 24 hours.

NO it is not. Inflation does not mean growing money supply. It means money supply growing faster than the real economy that transacts on that money. Bitcoin money supply may be growing but not fast enough to accomodate the demand. So it is deflating.