2.  "Also, should the number in my I/O buffers be the same as the number of my ASIO level of my Focusrite interface? Meaning if I change one, should I change both settings?"
 
I would think the answer to this would be yes, the two should match.  If it was me, I would change the settings on the Focusrite first, and then see if Sonar settings change when you click "apply".  I don't know if they will match exactly, but if the settings in sonar change, I would leave them.  sonar could be reading your sound card settings and making some adjustments...
 
If you can change Sonar's buffer or samples settings independent of your soundcard (I cannot do this with mine), and sonar's settings don't change when you apply the Soundcard's changed settings...then my first inclination would be to match them both (manually).  (edited)
 
BTW that video posted two posts up was very enlightening.

Maybe I don't understand your question right, but if you're referring to the I/O Playback and Recording Buffers,
these settings are not related to the audio driver settings and therefore don't have to match.

I/O Buffer Size determines the buffers which are necessary to write to and read from your hard disk without getting dropouts.

In projects with many audio tracks, where a lot of audio files play simultaneously, raising the I/O Buffers from default 128 to 256 or 512 (KB) is often needed to avoid dropouts, even if your audio device driver settings are already set to a higher latency setting of 1028 samples.

For projects with a moderate audio track count, the default setting of 128 KB I/O Buffer Size should be fine.
 

"Use reported latency" insures all audio tracks are in sync. YES you want that checked. You can check, as has already been suggested, with a "loop back" test. Sonar will have it spot on, you don't have to worry about it.

if you increase the sample rate in your ASIO panel with a track open it speeds it up to ridiculous proportions. XD
 

i was having fun with this the other night