What were the two most important issues at the Constitutional Convention? How were they resolved? What ideals were reflected by the compromises?

To me, the two
were

• How to divide up representation in the
  Congress.  The dispute was between small states wanting equal representation by state
  and big states wanting representation to be apportioned by population.  This was solved
  by the Connecticut Compromise.


• How to deal with slavery
  -- would/could the slave trade be outlawed, how would slaves be counted when it came to
  representation in the House.  This was solved by the 3/5 Compromise and by the clause
  that protected the slave trade for 20 years.

To
me, the main ideal reflected here is the idea that unity of the country was paramount. 
They reflected the delegates' desire to put the desires of their own states second
behind the needs of the country as a whole.