I found a web post that may resolve a lot of issues reported with FCGI on ISPC3 by various users including me.
The solution there is to add the following to a vhost.conf or httpd.conf:
# Sane place to put sockets
However, I am not sure how we should go about adding the directives mentioned. In the ISPC3 Panel, we can control "MaxChildren" and "Max Requests."
What about the rest?