It's amazing what you can do by typing in the name of a graph on Google. I guess that's why my school teachers marked down my score if I forgot to label my graphs.
1. If it is a myth than poor people need to be educated on it because it is pervasive. Similar to the myth poor people generally have that if you get a ticket it is better to not show up than to show up and tell them you can't pay.
2. I believe it is not a myth but I don't have any proof available. While benefits are phased out as your income increases, I think the phasing out happens quicker than the increase. The chart the other commenter posted looks good but who knows.