Your local home improvement store should have these - stair wooden overlays -they come in several wood types . Then you wont need to sand your life away. Some flooring stores may also carry this product.

Did you try a heat gun and scraper to remove the tar? You don't need to get it hot, but warmth will often soften it enough to get it off

When we did my kitchen floor we found an emulsifying cleaner that I mixed with boiling water (my underlay had a papery surface over the tar) and poured on. After a couple of minutes the stuff just scraped off. Unfortunately, I don't know where to buy the cleaner but it was a grease control product from odo-ban. I'm usually skeptical about the "green clean" products, but that one was an absolute lifesaver