Please explain my meat dry curing observations
There are several variables that need to be considered to properly and safely dry cure meat...temperature, humidity, ph level, for example.  Just on the topic of moisture loss, however...you will not be able to tell simply by looking.  People who do this for a living can tell by touching...most of us weigh our product before hanging.  In general, when there is a 30% reduction in weight, the meat is properly cured (given that all of the other variables have been properly dealt with).

Meat getting harder means it is drying, however it could be drying too fast.  In this case the outside will dry before the inside has a chance to.  If this is the case, the meat will not be pleasant to eat, but more importantly you could have a potential safety issue.  Proper humidity and temperature will help control this....around 60 degrees F (15 C) and 60 - 70 percent humidity.

As far as salt goes, be sure to use some sort of curing salt.

I recommend reading up on the process.  Many things can go wrong and you can make you and your guests sick very easily.