No need to apologise .. I'll help as much as I can.

Yes, you didn't use enough salt because you didn't follow my suggestion but just guessed it. You can actually tell because of the wonderful open texture. Salt kills yeast. So no where near the poolish and experiement with quantities. A pinch of salt isn't 1gm let alone 7 gms or so, so wheigh it. When you put it in your mix you must keep it away from the yeast and the poolish before you mix. As salt retards rise you will need to allow it to take longer to rise and the longer time also adds flavour., If you don't weigh and keep a record of what you did you will forget and not improve your bread by experience.

Yes, the semolina isn't in the dough it is a sort of cheats way of getting the crispiness you'd get in a really hot oven but in a domestic oven. So on it's final shape you rest it on the semolina and also put some on your peel. instead of hard flour.