Are there other direct effects of the mycotoxin damage?
Unknown. There is no other discussion of the effects of the mycotoxin within Neuromancer, and no further mention of mycotoxins throughout the rest of the Sprawl Trilogy (Count Zero, Mona Lisa Overdrive). I'm also not aware of any mention of mycotoxins throughout his other books (and he's an author that does tend to re-use his own tropes).
E.g. did he become dumber?
There is no evidence of this; if anything, he is arguably making smarter choices by the end of the book than he was in the beginning. But that is presumably a result of his experiences and the therapeutic effects of confronting his inner motivations during the Straylight run.
There was also no mention of any physical effects (acne, rashes, etc. etc.)
Bottom line, we just don't know. If there were they weren't worth mentioning.