It's been awhile, but I used to be a regular on this forum over 10 years ago. I have a couple of questions:

1. I have a maple hardwood floor that is about 24 years old, and it's got some gaps in it. I'm going to fill them with WoodWise, but some of the gaps are very narrow and I don't know how much I can get it worked in there. Furthermore, there is a lot of dirt deep in those gaps, which can't just be vacuumed out. I can't get it out with a fine brush and cleaner either. If I can't get it out, I think that dirt is still going to be visible after sanding. Any recommendations?

2. I was going to just do a clear finish on it. However, I'm throwing around the idea of using TransTint (mixed with SLX to prevent grain raise) or another dye instead of a stain. I like the look of the grain better with a dye. Has anyone done this? Will it fade more from sunlight than stain will? I'll be using Bona Traffic as the finish since I had such great results last time I used it.

A thick putty knife could be used to scrape the gaps. Dirt will stain raw wood, so you will likely have faint lines where there were gaps.
If you can find Saman stain it looks great on maple and can be coated with any finish It is non grain raising water-based stain.