Crackling distortion

Your cartridge isn't properly aligned. I had the same symptoms until I figured out how to correct that.
Good advice above..
The first thing I needed to do was set the proper overhang using a protractor or gauge. By definition, the overhang is the distance between the needle and the center of the spindle while the needle is in a straight line through the spindle to the pivot at the rear of the tonearm. So you have to get down and sight it like you're aiming a rifle.
Next, the VTA. The face of my cartridge is 90 degrees to the top, so if I can get the face of the cartridge square to the platter, the arm and cartridge will be level with the platter. I used a block of wood (similar to dice) to check for square as I adjusted the height of the tonearm. My tonearm lacks any way to measure the height, so I used playing cards as shims to gauge the height at the rear as I checked the face of the cartridge with the wooden block. After I got things level, I checked and adjusted the azimuth using the square block against the left and right sides of the cartridge body till they were perpendicular to the platter. Finally, I used a tracking angle gauge to verify the cartridge alignment.
Since any one thing can affect another, after I was done, I rechecked everything until I had everything zeroed in.
Now the cartridge was flying straight and true.
Since tracking force can affect VTA, I did all of these things with the tracking force set to the cartridge's recommended tracking force on a non spinning platter with a normal thickness record on top. To keep the record and stylus from damaging each other, I covered the record with a piece of glossy, photo weight paper. The glossy paper allowed the cartridge to drift back and forth over the surface without damaging either the stylus or record.
The last thing I did was set the antiskate using a test record till the test tones played with the least amount of distortion.
Now finally the tone of the music is correct (VTA and Azimuth affect tone) and the record plays to the end of the loudest tracks without distortion.

The geometry of the dynavector 20X2L looks very similar to my Grado Sonata1. I don't understand how your method square's the thing up to the record surface. Eyeballing the face and sides of the cartridge till they were flush with the square block was rather simple. Adding or removing a playing card shim was a simple way to listen and adjust.

I used the Hi-FI News Analogue Test Lp which has three 300hz tones L+R +15db on side two. The first test band is the first track on side 2, the second band is in the middle and the third is the last track of the side.
These were the tracks that allowed my ears to zero in and minimize tracking distortion. I don't think I could have done it without them. Everything else was a guess before I realized how to take advantage of the tones and their position on the record.
In addition to the test record, the package also includes an alignment gauge and instructions.
I don't think I've set up "dozens of cartridges"
in my lifetime, but I have probably made thousands of adjustments, usually decreasing distortion in one area only to increase it in another.
I didn't use the record to set up or align my cartridge, I only used it to check my work and fine tune the anti skate and lateral balance weights. It was very helpful having the same tone repeated throughout the side. I don't feel as though the alignment has been optimized for one area at the expense of another.
Some people think Test Records are a waste of money that provide a false sense of security. I disagree. A well designed test record simply provides a reference tone. How it gets used is another matter.

"Now try this: having heard and understood just how your cartridge behaves across those test tracks, try making the same fine adjustments while listening to music. Your results will probably differ from the test record. There's a high probability that (slightly) reducing VTF and anti-skating from what's optimal on the test tracks will result in better sound on most records."

Maybe so, but I'm afraid to mess with success. I pretty much did all that (VTF, A/S, alignment) before using the test record to "trim" the distortion in the sound and music out.
If I were to change the VTF, I would most certainly have to change some other parameters as well, and it was such a pain. I haven't heard any problems yet so I'm going to leave things as they are for the time being.

Honestly, I love the way it sounds.

And now I appreciate why folks mount two tone arms on their tables and don't bother with detachable headshells.