Predicting the solution with the highest boiling point
The first aspect to consider is the van't Hoff factor. Thus #1 is first and #4 is last. Since both #2 and #3 have the same factor of 2, we must consider other properties.

A major part of BP is how many molecules of solvent are exposed on the surface layer. Therefore, the ions with the greater diameter should take up more surface area, decreasing the number of solvent molecules available to 'escape'.. decreasing the vapor pressure and increasing the BP elevation.
My guess is that the polyatomic ion is quite large in comparison and the deciding factor.

from lowest BP to highest
 #1,#2, #3, #4