Eventually when you come to resell, a pool is an added plus. But for your own purposes, emptying the pool and adding a deck over it with a hinged door and steps placed below would be great for storage (as per option b but bearing in mind you could revert). All the best for your lovely new home.

there is no perfect dimensions for an island. Try to organce space subdividing into smaller cabinets of 60x60 cms which is the max space for a structural division and works for seating area as well

Just because you want to use the space below the stairs, do not just add drawers or shelfs unless you reaalllyyy need it. I would suggest go for adding something green to your house. Its healthy by adding air purifying plants. These plants are nowadays available in most of the nurseries and moreover Green patch in the house gives a beautiful look to the house and is also good for eyes ( the green color). Below are few picture to motivate you for Green patch or Indoor garden.

So you want to construct the kitchen along the two 7' length walls facing each other and along the 9' wall that joins them? It can be done if the space is used practically. But first please share your floor plan to show the position of the doors and windows too. Only then can once figure out how best to utilise the space