When I was young and poor I baked all the bread my family of 5 ate, for several years. I baked yeast and sour dough breads with various flours.
So some hints: 1. Use good bread flour! King Arthur's or Hecker's brand, if those are not available look for a high gluten wheat flour, if possible unbleached.
2. Get good at making yeast breads first. Yeast is more efficient than lactoacid bacillus and will make bread rise better. Once you have made a few batches of nice home style white, then try adding in some different flours. I used to make oatmeal, rye and Anadamer bread. All of which are variations on white. None of them will rise as well due to the lack of gluten. Then add your sour dough to the yeast dough. Yes, you can get sourdough to rise without yeast but it will take much longer and occasionally fail. Adding the sour dough starter to a yeast dough will still get you the great sour flavor with the bonus of a better success rate.
3 There is no substitute for kneading. You generally can't stir enough flour into a dough to make a firm bread, you have to knead in the last couple cups. Your problem really sounds like not enough flour being kneaded in at the end. Your boule should be smooth and have a dusting of flour on the outside. You can over knead, if the dough starts to tear rather than stretch just let it rest for half an hour.
My first impression is that the towel might not be porous enough to let the all-important yeast and bacteria in. Try cheesecloth.
If that doesn't do it, here's the long version:
Creating a Starter:
First and foremost, a week isn't necessarily enough time to get a starter going full steam ahead. It can take as little as a few days or as long as a month. You're relying on ambient yeast and bacteria that are floating around in the air, and the amount of yeast and bacteria available varies according to location, climate conditions, and all sorts of other environmental factors. The specific species and strains of yeast and bacteria also vary from place to place, which is why San Francisco is renowned for its ssourdough - they have the best ambient yeast and bacteria strains. Give it time.
Maintaining a Starter:
Feeding Schedule:
As a general rule: Once your starter is healthy and active, bubbling, rising vigorously, and smelling sour, you have two options:
If you store the starter at room temperature, you need to feed it twice a day. Don't wait for the risen starter to collapse before the next feeding, because it messes with the ph levels and can make the yeast and bacteria less active. Every 12 hours, feed it.
If you store the starter in the fridge, you can go up to a week between feedings. The cold won't kill the yeast and bacteria, it just slows them down. Just make sure the starter doesn't get shoved into a super cold spot and freeze.
The feeding process:
Stir the starter, remove all but 4 ounces of it (you can either discard the rest or use it to bake something). To the remaining 4 ounces, add 4 ounces flour and 4 ounces of purified or bottled water (chlorine in tap water is bad for the yeast and bacteria, and most filters remove chlorine taste, but not all the chlorine). Room temperature starter gets room temperature water; refrigerated starter gets lukewarm water. Stir until no dry flour remains. Cover with a non-airtight lid. Refrigerated starters need to stay at room temperature for several hours after feeding so the yeast and bacteria have a chance to wake up and eat.
Best Answer
You should be fine. I would suggest using a container that creates more space between the cover and the starter. That way you won't have a mess to clean each time.