Re: Why does the water level rise?

It wasn't because the oxygen was being used up, though that's a good
guess.  Indeed the oxygen is being consumed, but the flame is also 
producing gases such as carbon monoxide and carbon dioxide, which will
replace the volume of oxygen lost.

You were right on the second count.  The candle flame greatly heated
the air inside the jar.  When the flame finally went out, the air cooled,
and as it cooled, it contracted.  A partial vacuum was formed inside
the jar, causing the water level to rise upward.