If you perform an nslookup command on the fully qualified domain name from your home system, which is using Google's DNS server with IP address 188.8.131.52, does it return the appropriate IP address? E.g.,
nslookup myddns_address.example.com. I.e., do you get the right IP address, but can't establish an SSH connection to the system? I'm not sure from your post whether the timeout is for the SSH connection or an nslookup. If it is for the nslookup, can you look up the IP addresses for other systems from the home system. E.g., does
nslookup superuser.com return an IP address? If you are, instead having issues with the SSH connection, though an nslookup returns the right IP address, do you know if the SSH server is restricting connections to particular IP addresses or ranges of addresses?