Qualified Reward is the percentage your maximum possible reward based on voting performance. This reward decays at a rate of 16.67% per month.
Estimated Rake Reward is the potential percentage reward you could receive based on the Qualified Reward percentage, the amount of PPY you have vested and your share of the total GPOS balance.
For more information see Participation Rewards.
Voting qualifies you for participation rewards but the actual amount you qualify for is also based on the percentage of your PPY balance you've vested.
Every time you withdraw from you GPOS balance there is a transaction fee of 0.01PPY.
Basically, vote more often!
The performance rating is based on voting performance, to have a rating of 'OK' would mean that you've missed voting for about three months.