After a few months of mixed results, I returned to alexandracooks.com advice and recipe for sourdough and still had issues with poor oven spring, and very difficult wet dough. After some experimenting I found what worked for me.
First, I powered up my starter by feeding and discarding three times. I deemed it ready when it had more than doubled in volume in 2 hours in a fairly warm room.
Next, I drastically reduced the water in the basic recipe. (we also confirmed that the scale is accurate)
I used a stand mixer with the dough hook for the basic mixing. Water first, then salt, starter and lastly bread flour.
300 g warm water
100 g fed starter
2.5 teaspoons salt
500 g King Arthur bread flour
Mix the dough until some of it pulls off the sides of the bowl, about 4-5 minutes
Knead briefly, then place in straight sided plastic bucket with measurements printed on the exterior so you can see what amount of rise occurs during bulk ferment. (Keep covered loosely)
Wait 30 minutes then do a series of stretches and folds. Repeat 4 times. After the last fold, cover and wait for the bulk ferment to complete. When dough has increased in volume to about 1 and a half the original size.
Shape and place in basket with tea towel lining using rice flour to prevent sticking.
Rest loaf for 20-30 minutes.
Place in fridge for 24 hours (approximately).
Turn out loaf, slash top, place in covered cast iron oven or Dutch oven with 4 or 5 ice cubes to generate steam.
450º for 30 minutes covered
400º for 25 minutes uncovered