Wood – Protecting old wood floor

This is an educated guess only because I can't really see or feel what you are describing. This may be old floor wax that has had something damp left sitting on it. Often in older homes folks would use old fashion floor waxes that will discolor or turn white with age, water, friction or heat. You may first try using a little mineral spirits or a mild cleaning agent with a polishing compound, such as Bar Keepers Friend with a soft cloth on a small spot to see if it will remove the white residue. If in fact this floor has been treated with a wax product, the entire floor would have to be stripped of wax, perhaps buff sanded and restained, then protected with a few coats of Urethane. Don't attempt to apply urethane until you have determined what is causing the white waxy residue. Putting any coating such as urethane over a waxed floor will bubble, peel, and create a mess to clean up. another test you could do would be to gently scrape a very small section of the white stain with a putty knife. If the material comes off easily it may be wax. it may be old varnish, but that would not feel waxy, but not out of the question. Let us know what you find, and we can go from there. Good Luck

Time = Money. And assembling these in a manner that won't cause you headache later is going to take a lot of time.

To make a tread, you'll need to laminate the floorboard together somehow, otherwise they will flex under the weight. Construction adhesive would work, but wood glue might be better. And don't forget to sand or plane off the finish before you glue them together because the glue won't stick as well to the finished face.

Multiply all of this by the number of steps you have.

Another method with slightly less work is to put down regular stair treads, then put your hardwood planks over the top. You need to carefully select the correct thickness of the tread, taking in to account the thickness of your planks and the nose molding. This is similar to what is described in the article you linked to in your comment.