Bill your biggest problem is the stuff you use, as you call it
Tongue oil finish , that stuff is just thinners and volatiles and no Tung oil at all, it will not build up a finish like the Tung Oil.
I have used Tung oil for many years already, and normally use the Polymerized Tung Oil, as it hardens faster and gives a higher gloss than the Tung Oil that is not treated.
I wipe from 2 to 4 coats of PTO (Polymerized Tung Oil) on my turnings, depending the wood and gloss I want to get, Black Walnut gets often 3 or 4 coats for the open grain it has.
The way I do this is, wipe on a liberal coat of PTO, wait 10 minutes and than wipe the piece down, removing all I can, let the piece sit for a day in a warm dry place, then add another coat, same as before.
One thing with open grain like Black Walnut, I will rewire the piece again in 20 minutes or so, as the oil will sometimes bleed out of the grain, and show up later as tiny bubbles.
After enough coats (2, 3 or 4) I set the piece away for a month or maybe longer IF I want to polish the finish, the PTO finish should be nice and hard by then and polish up well.
Here are a couple pictures, first one is from some smaller bowls from different woods,like Apple, Hickory, Aspen, Osage, Ailanthus, Black Cherry, Black Walnut, Elm and Maple, the other pictures are from Black Walnut.
As for sanding your piece now, I would hand sand with the grain till the scratches are gone and then add the PTO.
mixed wood smaller bowls.jpg Walnut bowl.jpg Black Walnut.jpg Walnut.jpg