What does it mean when your bread looks this bad...

Take and post some photos of your starter. Store it in a clear glass or plastic container, and take photos at regular intervals; this will take some patience of course, but so does anything with wild leaven/sourdough :). This will help you get more comfortable with your starter's behavior, and knowing when it is at its peak. 

I think you are on the right track with your previous post in that your starter activity is an issue.  Related to this, your bread looks like it's either significantly under- or over-proofed. The timelines for sourdough fermentation can be very long, depending on the activity of your starter and the storage environment of the dough. 

Those "mouseholes" are likely related to shaping. Yes I've had dough stickiness problems with Tartine as well. Be careful how much flour you use when you shape. Use a bench scraper to help you shape. The brand and type of flour you use makes a HUGE difference when it comes to stickiness and overall dough performance. Try experimenting with different flour brands.

I take 25 g of starter (usually stored in the frig) and mix with 50 g of  AP flour and 50 g of tap water, mix well and sit out on the counter over night. In the morning it is very bubbly looking and I add 50 g of flour and 50 g of tap water and wait 2 hours before starting the dough. The 2 hours is just because the Tartine recipie calls for using the starter 2 hrs after feeding. Other things to watch out for are trying to maintain as much air in the dough as possible. The last few turns during bulk fermentation should be gentle. When removing from the container, be gentle and detach it from the back of the bowl. Once on the table be sparing but sprinkle enough flour on the dough to be able to cut it into the 2 loafs without sticking to the bench knife. Flip the dough over with one continuous motion of the bench knife. Usually the dough adheres to the table a little on one side but just loosen it with the knife. Fold each dough in half so that only the floured sides are outside and use your well floured hand and the knife to shape into a round somewhat. The bulk ferment and proofing times will depend on your ambient temp. I found the book's times pretty true in my house (73 deg F).

have you tried it again since your last posting? Changes in your technique or ingredients?

Lloyd