Bosola? What?

"BOSOLA: Do I not dream? Can this ambitious age
Have so much goodness in't as to prefer
A man merely for worth, without these shadows
Of wealth and painted honors? Possible?"
(III.iii.275-278)

I am officially confused by Bosola. In the beginning, he is portrayed as this awful character who has gone to prison for murder and is willing to commit any sort of terrible act. Then he is portrayed as this useless spy who first poisons the Duchess and then is not able to figure out who fathered her children even though Antonio was right in front of him. It takes him three children (who knows how many years?!) to realize and this is only because the Duchess told him. The lines following the ones I quoted are praising the Duchess for basically taking Antonio in in spite of his social status. However, after praises, he still takes her into custody and at one point refers to her as a "low fellow" (III.v.18). I can't really tell if Bosola is honest AT ALL, or if he puts on different facades in order to get the information that he wants. Is he playing stupid? Is he playing nice? Is he playing evil? I really have no idea and I am thoroughly confused when it comes to his character. I think the Duchess had it best when she said, "Were I a man, / I'd beat that counterfeit face into thy other" (III.v.19) -- note that counterfeit means "mask" in this context. I think those lines best summarize Bosola because I don't think we have gotten anything that would reveal his true identity. Instead, he seems to be hiding behind different personas, different feelings, different masks.