I am sorry to hear about your troubles. I am not sure I can help in all questions at all, but I can offer a few thoughts.
As for the paros it sounds encouraging that most of them are eating and looking better. For the one that is not looking well, it is not easy to say what it could be. My experience with licorice gouramies is that they are not so prone to diseases, but odinium is something which can affect them. Of course other conditions as well, or reactions to too much stress and changes in waterconditions.
The clamping of the caudal fin in the chokolates and the one paro too me is probably just a sign of unwell being, – as far as I remember, chokolates really do this when not feeling good (totally folded caudal fin) – but the jerkyness might indicate that there is something really bothering their skin condition as you yourself also think. With the paros I would think that the change in water chemistry is mainly responsible for this, – however I would look carefully after whether they develop odinium. (Which is not uncurable with licorice gouramies if you have the right medication)
As far as I know, medication used in low ph water works much stronger, – and normally you should half the dosis. Maybe you did that already ? But I always think that medication in low ph and low conductivity water is unpredictable really, so I almost never use it. Only medication I do use is spirohexol tablets (works extremely well with paros with odinium).