First, you should take the filters off of the lens. The CPL really doesn't do anything for you and the Tiffen UV filter likely caused the washed out look that you are seeing in many of your images.
The CPL also reduced the amount of light entering the camera, causing you to use slower shutter speeds. It seems on many of your seemingly out of focus or "soft" images suffer from slow shutter speeds, according to your EXIF data.
In the bright sunlight, or when using flash, the f/5.6 lens won't hinder you at all. The only time that you really need a "faster" lens is if you are shooting in very low light. Not having the CPL on the lens would have made up the difference between a f/5.6 and f/2.8 lens.
F/5.6 to f/2.8 is two stops of light, so going from ISO 100 to ISO 400 would have the same effect (amount of light let in) as going to an f/2.8 lens. It will affect other aspects of the image, but the amount of light let in would be equal. Again though, that is not really a factor in these examples with bright daylight.
You have some great shots with great composition. I think this is the most important thing, since you can learn the technical aspects of photography pretty easily, but having an eye for a good shot and good composition is best when it comes naturally.