Are you saying that you tried uninstalling and re-installing he firewall component as suggested, and it has made no difference?
I would have expected this to have cleared all the rules/settings that you said you were worried you might have changed, and returned to firwall to default state (but as I said it's a while since I had the firewall, so I can't check this out).
(If it was actually firewall expert settings, rather than application rules, that you had altered then I guess avast might have remembered your settings and just reapplied them on firewall re-install.)