the problem with ordering online like this is that they will usually only cover you if teh fis harrives dead. any problems with the fish once it is in your tank will more often than not be blamed on your water or existing stock. wormer plus is indeed good stuff but tbh i doubt it will do anything to help the growths on the sev , as it is more geared towards dealing with internal protozoan parasites . it can help with external parasites , flukes etc but these are better attacked with a med specificly for this purpose.
easier said than done i know but try not to pannic , remember fish are surprisingly tough and once the problem is nailed down , a fish has to be pretty far gone to be beyond saving.
good luck with turning things around and dont give up..