Personally, I'd whack it just where the dying leaves are. allow it ot callous and plant it in good mix. Then remove all the dying leaves and you might get some pups growing from the remaining stem. The stuff that looks like salt is more probably a course sand as a top dressing.

I can totally understand the confusion!! I actually started out looking for that form of DE, but could only find the powder format first. Most of my plants seem to retain the DE rather well. I have a few older cacti where I have added more to the soil (below a top layer of scoria) when I water, and because of the small size it sinks into the soil with successive waterings. In my organic mixes, the powdered DE stays much easier, and acts as a soil dryness indicator for me as well. I've always been afraid of handling pesticides, especially around rarer species. Stapeliads that maintain a "jumping stem" growth form in culture need finer soils a lot of the time. For instance, I recently purchased a Stapelianthus madagascariensis that needs fine soil around the fine, small roots it grows at its various rooting points. Typical large particle gritty soils will dry out its roots and kill it. In my opinion, the trick to having a good finer gritty mix is maintaining a diverse particle size range. For instance, the finer mix version I use still has 60-80 percent larger particle sizes that are traditionally found in gritty mixes. The fatter Pseudolithos species arent that picky about growing media in my experience. As long as 70-80% of the media is porous lava material of some kind, the rest can be almost anything that isn't too rich or wet. I have used finer inorganics, DE, coir, and even mechanically minced/small particle sphagnum peat moss, and the only rot I have encountered so far has been from errant sprinkler water kicking normal topsoil mud onto a part of one of my cubiformis plants, but that was it. And the main body of that plant was unharmed and continues to thrive in ~40% fine, gritty soil. However, I do live in Florida, which has the highest average UV index in the US as well intense heat and humidity for 6 or 8 months out of the year, compared to most other US states. For instance, it consistently hits 90 to 100 here with 100% humidity from May to September. The more south you go in FL, the larger this range gets. In my hometown 150 miles further south, it's very hot and humid from about March to the end of September. I also live in an area with great wind exposure and by a lake, so I have a constant humid breeze. As such, I haven't had a problem with drying out due to clogged soil pores or lower levels of absorbent material, but rotting due to standing water in fine mix has been a concern of mine. However, maintaining a diverse particle size range helps alleviate this problem by maintaining excellent drainage.

Feeling a tad disconsolate at my gappy garden myself and pondering falling back on the faithful hardies...but really, I think you can do a bit better than the ubiquitous macrorrhizum...unless you can get your hands on the outstanding White Ness - a compact and very floriferous pure white. The wallichianums do rather well in shade...although I agree, I am heartily sick of Rozanne...but there are others such as the neat Sweet Heidi or the pink Syabru and also, Lilac Ice - not as prolific as some wallichianums but distinctly better than the pale Crystal Lake. There are some interesting shorter bloomers such as platyanthemum and, my new favourite, soboliferum which will do OK in shade. Maculatum, obvs, but also magnificum and Himalayense are sterling performers, good for a second flush with nice foliage. If you have space, there are some good oxonianums with larger flowers (Robin Moss in the UK has been doing wonders with this group) and Patricia is a good doer, even in a shade-y spot. I must also put in a good word for Red Admiral - huge leaves and a long season of bloom...although that screaming magenta might not be to your taste. Another astonishing find - the south african incana/robustums which, although do best in sun, will also perform in shade - there is a neat hybrid - Silver Cloak...although might be lacking in hardiness for a zone 6. If you have a very sheltered wood, you might take a punt on one of the Canary Island palmatums - great foliage...but needs space. Finally, better, to my mind than the seedy phaeums are the nodosums - glossy fresh foliage and a long season of delicate lilac blooms - Svelte Lilac is the cultivar which comes to mind. Completely forgot about those woodland stars - the sylvaticums. Have several of them - Birch Lilac, Mayflower, etc. Lovely, partnered with early anemones. eta - I have the lovely Rose Madder phaeum - the best of the bunch to my mind. There is a rather good pyrenicum called Snow Flake or something similar - a goodie for sure. I would probably discount the palmatum in a Z5 though.

When you water it, do you flush out the entire pot? Or do you only give it small amounts, so that it doesn't drain through? It looks like it's not getting watered properly, causing mineral buildup within the soil. That's most likely why its leaves are turning brown along the edges. Judging from your photos, the soil looks way too dry. If it were my plant, I would soak the entire pot in water all the way up to the soil line. After about an hour, I would drain the water away and then flush it with plenty of fresh water until the murky water runs clear out of the drainage holes. This would help to remove most of the minerals that have accumulated within the soil. This, however, is just a quick short term fix. I would repot it with some fresh soil as soon as possible; using a fast-draining soil that doesn't stay soggy, such as a mix designed for cacti & succulents. With the sun getting lower on the horizon, I would move it closer to a window that receives plenty of filtered sunlight. It needs to gather up as much energy as it can to recover, and it can only do that thru photosynthesis.