No need to fret, just epoxy it!

I decided to remove the 21st fret. To do this, the hyde glue needs to be warmed up. I used a soldering iron directly on the fret. After a few minutes, I began to feel the fret move. So I slowly began to work the fret loose with a variety of tools... a small pair of end nippers worked the best. Once the fret was out, I used a wet paper towel to clean up the hyde glue... and a 10 mil finger gauge with a paper towel around it to clean out the slot. Once this was dry, I took a new fret and epoxied it in.

I clamped it down for about 90 minutes. This turned out to be a lot easier than I thought it would be.

Now the fret is seated properly AND with the epoxy in the bottom of the 21st fret slot I don't have to worry about that crack getting worse.