Don't 2 pack anything. Think of it like a plastic bag covering the wood. If there is any penetration to that bag the sub straight is unprotected and can not be repaired. I have a scratch on my jarrah bench that I will repair in the next day or so and will post the outcome.

For the Finish go with a 2 Pack Oil Based Polyurethane, can Last well up to 30 years depending on Brand and Traffic over the floors, we use it on some of the Bar Tops we have Done and it is Bullet Proof. My Favorite part of it is its easy to clean. And a Secret way of Polishing small areas is using Car Polish and a Rag and brings it up like new.. only down Side is maybe after 10 years or So it MAY start to Yellow. You can also get different types of Finish either High Gloss or Normal, again Depending on Brand. We Used Wattles 2 Pack Polyurethane 7008

Hi why don't you install the spotted gum floor on the staircase? you can just order a plain staircase from the stair company, and the flooring installer is able to lay spotted gum floor on the staircase. The stair nosing can be customized by using the same spotted gum floorboards. That way you will have a flush finish through the house space.

Assuming that pic is your house , and without knowing anything about the rest of the house , or you , I'd go old-school , and do that wall in a rich red / almost maroon wallpaper with a 5mm wide gold stripe say every 100mm . But then I don't like grey .