Here's a link to a recent forum discussion on hiding the Null first column, though I don't believe it will work in your circumstance since you are using Measure Names above the date and Tableau doesn't like to be inconsistent about column displays.
As for hiding the circle marks, you have to have a color that matches the background of the worksheet, and change the color calculation to add that as a fourth option. Tableau defaults to white as a background and that is not available as a color, so if you want to keep white then you have to make a custom color palette, using thse instructions:
It looks like you have halos turned on, you'll need to turn those off as well get a true background.
Message was edited by: Jonathan Drummey An update: I'd had a brain freeze and forgotten that you can make a white (or other custom color) much more easily by going to Edit Colors..., then double-clicking or right-clicking (both work) the color/valuein question to bring up a custom palette for that particular value.