I imagine the MP and BP are nearly the same. I mean, if it transitions from a solid to liquid, then it will transition from a liquid to solid at the same temp in a reverse reaction right? I guess at equilibrium, if there is such a thing, same amounts would be melting and freezing.
Dissolving a non-volatile substance decreases vapor pressure of the solution and thus increases boiling point because there is simply less volatile substance in a given mass of solution. It's a dilution effect. That means adding a volatile solute would decrease the boiling point of that solution.