Ok, thanks again.
Regarding gif interfaces. I now figured out how to do 6to4 using gif instead of stf0/stf1.
I am unsure wheter the /48 prefix instead of /16 will increase the latency. I still have to figure out how to circumvent this.
I followed http://ipv6int.net/systems/freebsd-ipv6.html and configured pfsense using the webinterface accordingly.
interfaces/assign/gif/"+".
wan/gif remote address: 192.88.99.1
gif tunnel local address: 2002:[myipv4address]::
gif tunnel remote address: 2002:c058:6301::/128
save.
Then I created an opt interface, assigned gif 192.88.99.1 and configured ipv6 only with an address of gif tunnel local address: 2002:[myipv4address]::1/48
Following the same method for the other interface, while the first is using a default gateway of ::192.88.99.1 and the other just a gateway of ::192.88.99.1 did the trick.
I am still investigating…