Is this F13 ? The postfix version doesn't match F14's postfix.
When you want to use epostfix, instead of the sendmail default, then you need to select this as the MTA alternative
Applications->System Tools->Alternatives Configurator
Select "mta" in the left column, and postfix in the right. selector button.
Then reboot or restart all the related services.
I compared your main.cf to mine and I'm not seeing, I' m not seeing a problem.
These are the permissions in that lock file I have ....
# ls -l /var/spool/postfix/pid/inet.smtp
-rw------- 1 root root 0 Nov 22 17:14 /var/spool/postfix/pid/inet.smtp
But that November date implies i'ts not used or at least not re-written.
Be sure to start the service with (as root)
service postfix start
or by reboot. If you manually start the various services as root oit may create files with wrong ownership.
The error messages you post have "localhost" as the system name. You need to set a valid system name.