Blacklight: Retribution XP required per Level?
Solution 1:
With respect to XP required per level I have data here. Worth noting, you'll see some anomalies such as the one between level 7 and 8. I'm guessing this is due to patching.
To subjectively answer your second question I've found that KC and SIEGE give way more XP than the other game modes (especially SIEGE) due to your base XP being based on your CP for the match.
Solution 2:
Don't know how accurate that chart is, but here is one.