Hello, my name is***** and I have over 20 years of experience as a veterinarian. I am sorry to hear that you got off on a less than ideal start with sick kittens.
Unfortunately both giardia and ringworm can be hard to get rid of. And ringworm especially can take weeks to months of treatment to successfully treat. If you stop too early all of your work will be for naught, and it will be even more difficult to cure.
I suspect that the powder is fenbendazole for the giardia parasite.
I am sure the ointment is an antifungal.
I would continue the lime sulfur dips every 5-7 days. If he is a long haired fellow shaving him to get rid of the spores in his coat and increasing the dip penetrating his remaining coat/skin surface may help. In many cases with using the dip you don't need to apply the topical too. The dips can cause lethargy but they have been proven to be more effective than the topical ointment, so if I had to pick one over the other I would pick the lime sulfur dip.
I'm not sure if the pill that they are taking is Metronidazole for giardia too, or whether it is oral medication (antifungal) for Ringworm (griseofulvin or itraconazole are two common ones). All of those medications tend to be hard on their stomachs and can cause nausea and loss of appetite, and of course that will make him feel less like playing and more like sleeping. Antifungal drugs can also be tough on their liver. If he is taking griseofulvin perhaps a switch to itraconazole will be better tolerated.
If he is taking metronidazole perhaps that can be discontinued since he has already had it for 5 days and he had fenbendazole.
I know it is hard to see him the way he is but long term continuing treatment is best. As long as he is continuing to eat and his liver enzymes remain relatively normal I would continue treatment.
Please let me know if you have any further questions.