General sourdough questions and debugging

Hi,

I've tried to get a starter going for months now and I seem to have failed/been impatient and irregular with the feedings. The only thing I found to have worked is a lievito madre - a white flour low hydration starter. I made it using white flour and some greek yogurt (I'm from Europe and where I live we have flours by type numbers, this is type 550 and it's a fine white flour). Feedings are 2 parts starter, 2 parts flour and 1 part water, by weight. This gets pretty consistent results in terms of rising the actual starter, though it takes about 8 hours to get to the peak volume.

My first issue is this - my sourdough doughs are no where near as tight as the ones leavened by industrial yeast. I try to tackle this by a lenghtier bulk rise and more folds, whenever I'm ready (or I think I'm ready) to bake and score the dough, it spreads quite I lot. I can get a decent oven spring, but I believe there should be more spring than there is now.

My other issue is I can never get even a similar crumb to what I'd get with an industrial yeast. My sourdough is always chewier and gummier. It's fully baked, but it always seems sort of wet. I don't know whether it's due to the acidity which is also something I want to reduce as much as possible. Once my bread is baked, the holes do look gelatinous as I think I saw they should, but the rest of the crumb is just not as light as I'd like it to be. It also seems very difficult to cut without the crumb tearing.

Would I get better results if I was to up the feeding times to 2-3 times a day, as opposed to once a day? I also keep the starter in the fridge for most of the week. 

Thanks to everyone who takes the time to debug my issues :)