I've done this before with only access to the WAN.
1st. You started off right by disabling the firewall
pcftl -d
then connect via the wan to the Web GUI. Don't add any firewall rules at command prompt.
Go to firewall rules > WAN tab
delete the "block private address" wan rule. Its at the top. Grey.
Now add a pass rule on the wan to allow you to access the web gui via the wan
at this point you can pcftl -e
Now, very gingerly change your pfsense password to something secure.
Now, at this point I'd configure SSH on the WAN and probably OpenVPN also.
Then I would delete the HTTP / HTTPS pass rule you created on the wan
From this point, if you are doomed to only have access via the WAN, at least you can do it securely.
For anyone who may be wondering "why the heck did you ever do this", its because I was using pfsense only as a VPN server and was forwarding ports from a ddwrt router to a VM running in vmware player. Just to give a friend access to his LAN remotely without him needing to buy any hardware.