Is monetary policy an all-encompassing term like thermodynamics? What specific monetary policy laws have empirical constants?

Thermodynamics is actually a fairly good parallel of economics, a dynamical system which has emergent laws. There is a fixed function which describes optimal monetary policy, we still don't fully understand that function but we do know some of the primitive functions that make it up and the relevant variables for the system (EG we know that the Marshallian K provides a way to understand the impact of monetary policy on asset prices). I would compare this monetary function to the GUT in physics.

The last recession was the first opportunity to test many ideas in monetary theory in many decades, lots of old ideas have been thrown out and new ones brought in to replace them.

Does monetary policy exist outside of human perception?

Economic policy rides on the aggregate, the significance of single actors is basically nil.

so is a minimum wage law not a direct link between monetary policy and wages?

That's fiscal policy rather then monetary policy. Monetary policy is concerned with money, fiscal policy is concerned with spending.

Fiscal policy is far more shades of grey because "optimal" changes meaning depending on the significance you place on specific variables. As an example we have optimal tax theory which establishes the Pareto optimal form and rates of taxation (EG given a revenue demand of $n you should impose these forms of taxes in these ways) but while this certainly does optimize growth & welfare there are political considerations beyond this, if inequality was a concern which the tax system was used to resolve then optimal would encompass more then simply Pareto efficiency.

Monetary policy functions at a higher level, its unconcerned with the welfare of economic actors but simply macroeconomic stability.