Very new person- Is lack of holes & chew a hydration thing?

Hello

i am brand new to bread baking but sourdough is my favourite to eat (& is meant to be better for your digestion etc etc), so I bought some 30 year old rye starter from eBay and began. (Photo of Brown bread)Turns out I’m not into the taste of rye/ how dense it is, so I have made my own white starter using organic strong white flour. My first white sourdough loaf was ok, holey but flat (photo of holey white loaf) but the 2nd one I made (photograph of dense white loaf) was like normal bread - cumby and not holey. If anyone can answer my questions I’d be very grateful:

1. Are the big holes due to hydration- eg a larger % of water to flour generally means bigger holes?

2. What makes bread chewy? Is it the yeast and therefore the quality/how fermented the sourdough is?

3. I use a small tin of water in the bottom of the oven to create steam (although I have read this will never be enough to achieve a proper crispy crust) but my crust is too dark and bitter for my liking (husband loves it though!) but I’d like to know the science behind how to get a thin, paler, crispy, chewy crust.

4. I’ve been using the BBC Good food sourdough recipe where the second prove (unsure of terminology) is overnight in the fridge. It certainly doesn’t rise anymore for doing this, but I read that slow and steady = more flavour so did it anyway. Should it rise further in the fridge overnight or is it just to let the flavour develop?

5. I read that always leaving your starter Out if the fridge isn’t good and makes it too sour. Is this true? 

6. My rye starter (I keep 2. The rye whole wheat one I don’t like & the white one I created, that’s bubbly and happy but doesn’t seem to grow inside the jar much) now has a skin on. Should I throw it away? Or scrape it out of the jar?

7. When I said I just cover my mason jar with a piece of muslin & elastic band, to breathe, the man in my local post office said I should have a lid on (he mentioned tank fermentation (?!). I think he’s wrong or I would have to burp it regularly - am I right or is he?

I'm so sorry for all the questions it took me a while to find a forum.

Again, thank you for any help or advice :0)