Without knowing the actual finish it's hard to say which is best for you. There's usually not much Tung Oil in Tung Oil finishes and polyurethane can be solvent or water based. In general polyurethane finishes are harder, more brittle and vegetable oil with polyester resin finishes are softer less brittle but it depends on the proportion of the ingredients. Of course the most critical factor is the hardness and cut of the wood.

I have to say in regards to Waterlox: it is a wonderful finish when first applied. For the record I have laid yellow/heart pine and used poly to finish, I laid 900sq' of eastern white pine and covered with Waterlox. We built our own home 4 years ago and used waterlox original on the entire 900sq' of the downstairs. It gave is a yellow orange tint which is eactly what we wanted. It did darken over the 3 years we lived there as when we moved last week and lifted the rugs there was a very noticable difference in coloration. Application was horrible. I used a quality paint respirator in january. Since it was cold I had the windows closed. Eyes burned so I used goggles. When I would take the respirator off to readjust etc the fumes almost knocked me out. After the 4 coats over 2 days I shut up the house (opened windows at timed intervals to allow new air in). About 3 weeks later we moved in and could still smell the waterlox. A few days before we sold our house I did some touchup work since our yellow lab left several claw marks down below the finish. I simply put a little waterlox on a rag and applied by hand the 1'x1' area. You could smell it upstairs with the door closed. We had to open windows in january. Waterlox finish very much resembles poly. It never chipped on us but had the same type of appearance with the scratches. Repairs. Don't let anyone fool you. If you have a dog scratch your floor and it is deep you now have fresh unstained, unweathered wood showing. It will look very white next to the tinted weathered finish. You can apply new waterlox but it will not tint the scratches to match the finished side adjacent to it. It will reseal it and tint it a bit but you are going to see the scratches. Not as bad a poly, but you will see them clearly. Fast forward. Economy goes bad, decide to sell our home and purchase a cheaper fixer upper and try to pocket a little cash in case of job loss. The new home has pergo, yuck. I have already found a dealer for red pine this time. (should be a bit harder than the eastern white pine we had in the last home.) Plan on installing red pine in the entire house less the 2 bathrooms. Equates to about 2000sq'. The big debate. Tongue oil or more waterlox. We did lover the finish of the Waterlox and always got great compliments on the floor from guests. I don't really want to evict my family(young child) from the home for 7-10 days while the new finish gases off while drying. I have heard mixed reviews on the citrus solvent as being almost as bad for you as mineral spirits. I loved the finish of the waterlox and it did bead up nicely and cleaned well. I have never used the tongue oil and hope I am not making a mistake by taking that route. We love the matte finish of the waterlox along with the slippery feel to it. Does the tongue oil leave a smooth slippery texture also or do you feel the wood grain more? I have used a marine based tongue oil on a boat I built and that was not something I would want to walk on every day.

Keep at it! I cant wait to see how this turns out. We have a 1897 farm house here in TX that has floors similar to you. We are not sure the wood, as it is painted, and has been since my folks bought it back in the 1980's. I have not yet had the time to start the stripping process but I would love to one day. This house has a lot of history, as 11 children were born and reared here. I am afraid of all the sanding, to get some boards even but I want to leave some of the wear, as it has character. One room at a time may be the way to go. The bead-board was once painted grey (by the previous owner) like the staircase the original was stained (one room upstairs still is)and we painted it white. The banister is original. The treads are all hand cut by the builders. I want to restore them first. Here is the house itself with new Hardie-board siding

I don't have any experience with this, but my intuition and experience with tung oil says that you probably should try to get as much of the other oil off as possible, by washing with something like TSP, followed by a clear water rinse. then just coat. Tung oil can be over coated with an oil-based primer and then painted. For a more educated response, try emailing your question to customer service at Lee Valley, who sell tung oil and give excellent service. Their address: customerservice@leevalley.com