Yes, I understand. If you can get meds faster, the better. However, let me know if you need the flubendazole. The offer stands if and when you need it.
Yes, fendbendazole does not kill shrimp or snails from what I know, unlike flubendazole, but it is to be used in feed, not in the water. I wouldn't have any idea unfortunately on dosage. Flubendazole however, is also safe with any fish, anything older than a week and it works for fish that have stopped eating too, as it does dissolve in water.
It is very likely though, despite my recommendations, that either fenbendazole/levamisole(whichever you can get your hands on) or/and prazi will work for your skinny loaches. You'll just have to see which.