for some reason I do not see any pictures. If your leaves are still wilting, you might need to take it out of the pot yet again to see if it is continuing to rot. Clay (unglazed) pot are best, no drainage stone in the bottom of the pot as this tends to create an swampy anaerobic layer just above those drainage stones. Quick drying soils such as a cactus mix with you adding more perlite to it. NO direct sun while it is trying to recover, bright filtered light. A picture would help.

I've been trying to upload photos but it's buggy for some reason. Will try again in a bit. I do fine with other succulents, just feel ridiculous with this one as I can't seem to get it to work.

Bantel's are more sensitive to over watering in my experience.

this might help
http://forums.gardenweb.com/discussions/3142320/bad-news-for-bantels-sensation?n=9

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This is how it looks currently...

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This is how it used to look, much more rigid and healthy.

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You can see the extent of the drooping pretty clearly in this one. The very thin long leaf on the right held itself upright until I started messing with the different pots.

Let me get the sequence right the middle picture under the window in the plastic pot is before. Then the pictures in the terracotta are current, or second repotting? How did the roots look on the first potting? I as, because the soil in the plastic pot looks damp (dark color). Well, you know that the roots are mostly gone, so no matter what the time line, root rot is the issue. I'm concerned that you mention every time you water more leaves get droopy. How does the base of the plant look? How parched do the leaves look? I'd bring it back inside and keep it out of direct sunlight. How moist is the soil right now? in pots the bottom is always wetter than the top. You should stick you finger down as close to root level as possible to check it (or use a moisture meter or a wooden dowel) You only want a little moisture, nothing damp. Not sure if very dry will do more harm than good or vice versa. I would aim for let it dry than light moisture and let it dry. As to a scheduled, You best forget that for now and check the plant every other day (not that you are watering it), but this guy is in the equivalent of ICU. Any further drooping, I would recheck the roots. That is about all I can think of. Good luck and keep me posted please.
Fred

Wow, thanks for this great advice and trouble-shooting. I killed a really cool agave last year and I am feeling dumb about potentially killing another cool plant, so I appreciate the help!

Correct, the plastic pot is how it came to me and the terra cotta pot is the current planting. The middle planting before terra cotta was a really tall glazed ceramic pot, which looked awesome but it was all the wrong dimensions and materials of course! For the first transplant, it wasn't rooted all the way to the bottom of the plastic pot yet but had more roots than currently, and had some pups that died off when it was in that big pot. Now it seems like it is rooting somewhat, as when it was first in the new pot it wanted to fall over and now it is decently firm in there. I dug down and the base of the plant doesn't look rotten. I transplanted it about a month ago. Maybe that was the last of the rotting issue and it's leveling out.

Can I use pumice instead of perlite if I have it on hand? If perlite is better I can definitely go get some. It is in what they called a cactus mix but could use more drainage as it is fairly moist down into the soil. It has been cool and humid (relatively for southern CA) so there has been less evaporation. Since it doesn't have many roots currently, I think I will try digging the perlite into the current pot rather than completely transplanting, to lessen the disturbance and shock on the plant.

It's currently under a UV-filtering shade--I was hoping the bright filtered light would help.

Ok, that's enough rambling for the moment, thanks again!

What kind of soil is it in? Pumice should work. There are volumes on the topic of soil here on this site. Mostly
the recommendation is for making your own soil with an exotic mix of
pine bark, grit such as pumice or crushed granite, something called
turface and on and on. For just a few plants that is way too much
trouble. I've been growing Sansevieria in Miracle Grow cactus mix which
I add perlite to ( would love to try pumice sometime where do you
get yours?). At the moment you'll want to water carefully, allowing the
soil to dry say an 2 inch below the surface before watering again. Water so the soil is just moist. On a healthy plant
you want to water thoroughly allowing the excess to drain away. This gets all of the soil in the pot moist and also flushes some of the mineral salts away too. Your plant currently in not healthy, so we want the plant to have enough moisture to work with yet allow the soil to dry out long enough that rot does not continue. Resist the urge to water, we all have that urge LOL! No schedules check the plant if not daily every other day till it is comfortably over the crisis. I'm not sure it is a good Idea to digging in the pumice, unless you are talking about a
scratch it into the surface soil. I would see how your current soil dries with your careful
watering regime before doing anything.

As
for the UV shade, a gentleman named Al addressed this issue some time
back. If I remember correctly it is OK, but I'll have to try to find
that thread and get back to you on it.
Fred

http://forums2.gardenweb.com/discussions/1480695/low-e-windows-effect-on-plants?n=34