if the poo is white and stringy, the chances are he got hex or hexaita... or he has just constipation! looking at current photos, his head is shrunken! use the epsom salt soaked food for two three days. and observe. Read more about hex in this forum...
the wound seems developing a pimple as per photo, but these types of wound can happen due to parasite...
more and more water changes and temperature at 86F.
read more threads about hex, pimples or parasites and u will gett full treatment idea!! all the best