First Time Sourdough Attempt - Need Help

Hi All,

First just want to say what a lovely resource this site is, thank you.  I keep reading up on starters and feedings, etc. but I'm not sure if it's because I hated math class, but I'm getting super confused on hydration levels, etc.  (I know it's super easy for others, don't hate!)

I've been baking bread for about 3 years with great success - from prefermented dough to sweet dough, etc - literally everything except natural starters.  I bought a book and followed the steps to a T to make a firm starter.  here's the recipe - now I forget the initial amount on day one (I think it was 100%), but here is the feeding schedule, every 24 hours for 10 days:

69 g active starter
153 g room temperature water
270 g unbleached all purpose flour
30 g whole wheat flour

so - you can see that this makes a total of 522 grams of starter which you have to toss 453 grams of it in order to keep feeding, le sigh. Food waste kills me.

Now after the initial 10 days, I started keeping 69 gram portions in the fridge in little plastic containers in the event I had an epic fail so all that work over the past week and a half wasn't for not. 

So 10 days were up on a Thursday morning - bake day was Saturday so I actually fed for another 2 days - so 12 day fed starter ready to go Saturday morning.  I used this Pain de Campagne recipe:

126 g firm starter
506 g water at 80 degrees F
704 g unbleached all purpose flour
19 g fine sea salt or non-iodized table salt

Recipe is basically: mix, autolyse (i think that's the right word) for 20 minutes, then add salt, mix for 6 and then rest for 30.  Then, 3 sets of folds and stretches every 30 minutes followed by a 2-3 hour bulk rise.  After that, pre-shape, sit for 10, shape into boule and put in colander for another 2-3 hours.  

Saturday - total epic bust.  I do not have a banneton (I used to, but it got infested with bugs, yuck) so I used a towel lined colander.  Well the bread stuck so bad to the towel that I basically had to rip it off, 20% of the bread coming with it.  I went into panic mode and just threw the bread into the 450 degree oven on a stone.  Well, it didn't turn out.  Flat like a pancake and SUPER gummy and like iridescent inside.  Top crust though, delicious.  

Sunday - after reading the forum, I bought rice flour and dusted a linen towel instead of a cotton towel.  I also decreased the final rest to about 45 minutes since I was nervous that I overproofed the dough.  The bulk rise I kept at about 2.5 hours.  This one looked okay great oven spring- although it did spring mainly on one side in the oven - it broke on the bottom left even though I scored the top in an asterisk.  The scores also filled in.  For steam, I used a bread pan filled with water and a dish towel (which I read keeps an even steam going) and I also spritzed the oven with water when putting in the dough.  I also raised the temp a bit.  I was SO excited to cut into the bread - but when I did, there were GAPING holes like 3 in a row from left to right.  The dough had a very glossy iridescent look and was gummy on the bottom.  Into the trash it went.  It was a rough weekend since I typically have SO much success making bread - I was really upset and haven't attempted again (it's been almost 2 weeks). 

Starter is resting in 69g portions in the fridge.  Does anyone have any suggestions on a. does this recipe look okay, b. what did I do wrong, c. how could I improve, and d. are there better recipes since I can't stand throwing away so much flour?  I went through a 5 lb bag just from making the starter, and I don't want to do that in the future.

I really appreciate any help you can give, thank you!!

Renée