the money supply can remain static and the CPI can increase and that would result in inflation. Inflation may very well be a system of measurement but ratios are still scalars and thus numbers. We can get more in depth in numbers theory if you would like.
http://en.wikipedia.org/wiki/Inflation
An empirical example of this is the inflation in 1978. That was a direct result of OPEC raising oil prices and very little to do with the fed lending money.
Furthermore nobody saves in todays economy. While inflation impacts current capital it does the same for current debt. Only really rich people save in any serious amount. Everyone in debt has an easier time of it.
It also does not suddenly kick in once a threshold is met. Each additional dollar added has an incremental effect. Its called integration.
Thats simple supply in demand. One person spending $1 is an increase in demand as are 4 or 6 or 10,000. They are additive.
We already have listed the inflation rates for this year in this thread. You're assertion on stock values is also less than wholisitc. Sure the money dumped in the economy has an effect but its not the total effect.