I'm finding from http://canyouseeme.org/ however that "Error: I could not see your service on 51.9.205.72 on port (80) Reason: Connection timed out" however.
I found the problem. My Pfsense settings were fine but I had double NAT because NAT isn't automatically turned off when you set the TP-Link TD-W9970 to modem mode.
I sorted it by just opening the ports on my modem to my Pfsense router.