>>"I actually need to access RWW using the public IP address. "
This will not work with SBS 2008, you could with SBS 2003.
You need to have the certificate, the FQDN to which you connect, and the external DNS record all agree.
By default SBS uses remote.mycompany.com to set up the server and certificate. You need to set up an external DNS Host for remote.mycompany.com pointing to the IP of the server. This will not change your other DNS configurations and you can still use your external Mail service. You can change from the default "remot....) if you like when running the "Set up my Internet Address wizard" which must be done. I assume you have if the certificate installation package is in the folder.
If you are using a dynamic IP for your public IP you will need to subscribe to a DDNS (Dynamic Domain Name Service Like no-ip.com or dyndns.com and purchase their Plus managed DNS service or Custom DNS service, respectively, and move your DNS records to this service.,
