About the Part Time Jobs...

Does the level of your profession determine the quality of your reward and bonus reward?

I've noticed you get the bonus about 50% of the time too.

I'm not sure about the bonus, but it definitely determines the reward. If I do Mining on a character with low level mining, I get opal ores. If I do it on a character with high level mining, I get high level ores (last one was dark crystal).