gpm, is it possible that he has developed a lesion on top of the fatty cyst? The type of eruptions you describe sound very simuliar to our cat who was only positively diagnosed in the fall after we did biopsy. His eruptions actually damage his skin, they are deep and the scabs adhere very tightly, there is bleeding and if really big (size of coin) they look like burnt skin. However since merc, my cat seems to only have smaller lesions now, not that I advise merc, in our case merc brought out mouth lesions that had to be removed to stop the cat from choking to death. Perhaps his present problems are not as closely linked to the eruptions/tumour?
It seems to me that the ars has been benificial, perhaps 200ch was a little too intense? If his appetite improves and nothing major is happening, perhaps it would be best to wait and ride it out?