To piggyback on what others have said... Don't scrimp on quality when buying filters. FWIW, I use B&W too.

Regarding wide angles and uneven polarization - polarizers are most effective when the sun lies at a 90° angle to the optical axis of the lens. Angles more or less than 90° diminish the effectiveness of the polarizer. Depending on the position of the sun in relation to where the camera is pointing and how wide the field of view is, portions of the sky in the field of view could have varying degees of intensity in the polarizing effect across the frame, resulting in an unnatural uneveness in the color of the sky.

A 17mm lens with the 1.6 crop factor is equivalent to a 28.8mm lens in full frame and has a FOV of 74°. I thought that was considered wide angle?

I happened to stumble across these filter wrenches a few weeks ago. You may find them useful. Check them out here and here.