Hi! I would love some feedback on my bread. What I would mostly like to improve on is an more open crumb, as right now its pretty dense. Also, I often have the issue that my bread breaks at the bottom sides. Anyone know how to fix this or what causes it? I am however open to any feedback! So if there is anything you think I could try to do differently, please let me know.

My starter is 3 Months old and I always bake the same recipe.  
**Ingredients**:  
110g sourdough starter, at least doubled in size (mostly 1:10:10 with rye flour)  
300g water  
500g flour type 550  
2g salt  
**Instruction**:  
mix all the ingredients (I also mix the salt in right away, I didn’t notice a difference)  
wait 1 hour, then one round of stretch & fold, wait 30-45 minutes  
3 round of coil folds with 30-45 minutes wait in between  
let bulk ferment. after mixing the dough I varied the times from 6-9 hours. The bread in the pictures bulk fermented for 6,5 hours  
Form the bread and put it in the fridge in a round banneton.  
Leave bread in the fride overnight, times varied from 14-19 hours.  
take out of the fridge and directly put it in pre heated oven at 250 dregees. In the oven, I put a bowl of water for steam. I bake the bread on a baking sheet (not on the grid you see in the pictures). Score after 4 minutes, then keep baking for 21 minutes. For another 22 minutes, lower the temperature to 200 degrees and bake without steam.  
Put on grid for at least an hour before cutting open.

Thank you so much! ☺️

Beginner - how can I improve / achieve open crumb?