Could work. Get a piece or two and test finishes for something to compare. It's harder than cherry. There are other similar tropical hardwoods of different colors.

IMO the same as the floors.

I think I'd go with white oak to work with the flooring assuming your threads are white oak as well.

Treads are light oak and the stringers are stained black.

The treads were custom stained to match the prefinished floors so I don't think we can match the treads, but I will inquire. Perhaps pulling in the black from the stringer is the answer.

these are the stairs (without the cable railing). unfortunately, the treads are covered by you can see the color of the floor.

Black

Match the treads or stringers, but not both.