Look at the routers web page, Status/Device Info/Wan Section, is there a 192.168.0.# address in the WAN IP address field? Or a ##.##.###.### address?
Turn off all anti virus and firewall programs on PC while testing. 3rd party firewalls are not generally needed when using routers as they are effective on blocking malicious inbound traffic.
Is uPnP enabled or disabled when you have this PF rule set up? Test with uPnP disabled while using this rule.
Also please answer the questions presented to you by Hard Harry. The more we know the better we'll be able to help you solve this.