Can Table Calculations be used to create an average and percentiles on a histogram?

New to Tableau - although I have a copy of 8.3.1, difficulties and deadline pressure have kept us using Excel and SQL.  Would very much like to build a custom Dashboard that could be used to produce a weekly report.

It looks like a very nice product but always wind up spending hours trying to figure out the basics.

To give a sense of what we are trying to do:

We are doing a Dashboard that shows weekly occurrences of complaints in residential areas on vehicles with custom exhaust systems and car stereos and impact on communities from the resulting losses in real estate value, losses in real-estate tax, the additional time the houses spend on the market before they are sold and the discount (about 30%) that they are sold at when compared to equivalent homes in quiet neighborhoods.  Highest local losses thus far in western states are $500 million in lost property value and $22 in lost real-estate taxes. Future Health Care costs are also being tallied.  These are higher than real-estate losses.

After reading the on-line about Table Calculations, I still have quite a number of questions and am unclear as the the use.  It looks like a way to create aggregate calculations with user-specified grouping levels similar to a GROUP BY clause in SQL. 

A few questions:

1. What distinguishes Table (Across) from Table (Down)? Which is columns and which is rows?
2. Is it possible to do a Grand Aggregate such as overall average, median, 25th percentile, median, etc. over all rows?
3. Can the Grand Aggregates but displayed as vertical line markers on a histogram?  If so, how?  Can a table calculation be dropped on the Column shelf?
4. We would also like to show reference lines on histograms corresponding to the permissible decibel values used by The Member States of The European Union.  These are regulatory values (not calculated).  We would also want to specify vertical reference lines to show decibel level limits that impact health as specified by The World Health Organization (WHO) and OSHA.
5. Is it possible to add an axis title to the horizontal axis of a histogram?