To expand on what Charlie said, ProxyPass is a directive that goes into a "<VirtualHost>" declaration in httpd.conf. Consequently, for proxypass to work, your remote user must access your sme server using the domain name you have configured in proxypass. You can do this by creating a DNS entry in your public DNS, or by manually editing the 'hosts' file on the remote computer.
One way to do this would be to create a free account at dyndns.com, and establish a domain name something like "myfbproxy.dyndns.org", which you then point to the public IP of your SME server or to your existing SME server public host name using a CNAME record.
Then, you would setup proxypass on your SME like this (assuming your original commands were almost correct):
db domains set myfbproxy.dyndns.org domain
db domains setprop myfbproxy.dyndns.org Nameservers internet
db domains setprop myfbproxy.dyndns.org ProxyPassTarget http://66.220.149.11/
db domains setprop myfbproxy.dyndns.org TemplatePath ProxyPassVirtualHosts
signal-event domain-create myfbproxy.dyndns.org
You can also "ProxyPass" by hostname; you could set the ProxyPassTarget to
http://www.facebook.com. If you use a hostname for ProxyPassTarget, it must resolve correctly *from the SME server*.