what do you need caching for in the first place - nothing is static these days
What version did you install? What OS are you installing it on?
If you want to do MITM, then yeah the browser has to trust the cert your going to present.. Install the CA root in the browser of the cert your using.
Looking that the steps a bit deeper on that guide, did your cache get created correctly.. I don't think it would work with those chown only in the log section. Did you edit the .conf to enable chace?
# Uncomment and adjust the following to add a disk cache directory.
cache_dir ufs /usr/local/squid/var/cache/squid 100 16 256
Pretty sure its commented out by default.. etc..