Some applications do not work well with PAC file.
Are you using authentication ?
Based on your config, it seems that you are bumping everything, tried splice all?
Based on the problems I had, I found this:
Some apps can work with PAC file, others not.
Some apps can work with proxy authentication, like Kerberos for an exemple, others not.
So, sometimes you will see Access Denied in Squid, because the apps like Pokerstars for an example are not carrying credentials to the proxy.
Here, I have a Squid proxy with SSO, using Kerberos.
Some apps don't work if I set Direct at the PAC file, however, they do work when I set a bypass like this:
before_auth:
acl whitelist dstdomain .pokerstars.com .dropbox.com <---- This allow everything to pokerstars.com and dropbox.com to go through the proxy without authentication
auth_param negotiate program /usr/local/libexec/squid/negotiate_kerberos_auth -k /usr/local/etc/squid/mykeytab.keytab
auth_param negotiate children 100
auth_param negotiate keep_alive on
http_access allow whitelist <----- This allow whitelist before auth is required
acl auth proxy_auth REQUIRED
http_access deny !auth
http_access allow auth