Wow Andrew, this is a tall order. It sounds like the last owner not only did not take care of the floor, but in his misguided attempts to make repairs has actually done a good deal of damage. You have your work cut out for you!
Any finish you apply now will have to be removed when you do the full refinish job in the future. It will soak in in the areas that have already been sanded, and it may not stick at all in those areas that have a poor finish (sticky), only serving to make the problem worse. Trying to clean and cover the stained areas, deal with screws, and solve the sticky floor problem in a day is going to be quite a task.
How large an area are we talking about? How many square feet? Is it a large open area, or are there narrow hallways, dormers, etc.? how long before you tackle the entire refinishing job? Which might include digging out all that filler, resetting the screws (if they're really necessary) and plugging those holes with matching wood.
The reason I ask all these questions is because I think your easiest one-day solution might be to have inexpensive, "contractor grade" carpeting installed to protect what's left of the floor until you can do the job right. If your target "do-it-right-date" is two years or so in the future, then the carpet might be your best solution. If we're talking about a simple installation in a not too large area.
The carpet will buy you time and, at least, stop the deterioration of the floor until you can spend the appropriate amount of time on it. My only caution, those sticky areas. Some sanding might be in order before the carpeting goes down, or you might have trouble getting it back up!
My 2 cents.
We all die. The goal isn't to live forever; the goal is to create something that will. - Chuck Palahniuk