amavisd is a replacement for spamassassin, as it uses spamassassin internally. So running a separate spamassassin beside amavis makes no sense. Using policyd is not problem.
Regarding the error that you get, it seems as if you configured your postfix to require tls. But the internal connection to amavisd does not need tls and amavisd does not support tls for the internal mail exchange with postfix. So you should remove the tls reqzirement in your main.cf.