Do you still have the original images? Could you share them so we can better help you? I cannot say what would be better at this point - keeping this current segmentation result or trying to improve it - without seeing the actual datasets. That is the only way I - or anyone else - can actually, potentially help you in this case.
‘Create Selection’ will select the entire region… but won’t distinguish one pore from another. it’s just considered one, large area. You can look at MorpholibJ to see if there are any other tools that might help you in this case.
But again - I would share with us the original image - at least one for a good example - for us to better help you build an analysis pipeline.