Have you started construction or are you still working on design plans?

@ MB Builders, Yes please attach a floorplan. I would be happy to help you design a curved stair. Five feet width does not allow for very much of a curve. 3' is the absolute minimum on stair width - on your curved it may need to be wider to allow for a walkline to fit code as well. You can see our work on our houzz page or website. We build custom curved and wood stairs in our Seattle shop, and can installed them anywhere in the US.

I think it looks good on the paper but to make a code compliant staircase you will have to call a stair company have them do the layout and they will tell you if you have room or not and give you what options you have. In here you wasting your time. With that said, they can probably fit 3' landing with 2 stairs going down and doing 90 degree turn with 10 stairs, that will set you at around 8"+ riser height, here in NJ you can have a riser height 8 1/4" and min thread depth 9" so it might just work. You have to check your local code and see what the stair requirement is for your area and work from there. Good luck

it appears you need storage. I would get with a storage professional on how to best utilize the space based on your needs.