Siaopao, Setting up free/unprotected access is easy.
You have port 80 requests going to the router which then needs to route them to the NAS ip address (LAN address).
One step you are missing is to configure your router to redirect incoming requests to the NAS box.
IN DDWRT, go to NAT/QOS and setup a PORT FORWARD :-
*** WARNING:: this will totally expose your nas web shares on the net to ANYONE including google.
App: eg HTTPnas
port from : 80
protocol: TCP
IP address: your NAS LAN ip address
port to: 80
enable : <tick>
and then click ADD
So this will be the same as accessing your nas webserver from the LAN.
Similar redirects for FTP access..ie redirect Port 21 (FTP port) to the NAS...again...do you really want to do this?? At least with the webserver there is no ability to change/delete files.
I would suggest at the least changing the <port from> to say 8083 instead of 80 as anything from google to hackers will be FREELY ACCESSING your NAS box shares.
Reminder Note...this is TOTALLY unprotected...no password challenge...which is as NASLITE is designed to be...simple, unprotected access on a LAN.
As for a static IP address...no need...you would instead be fine with your no-ip account and your router auto-updating that if your address changes. I have always found
http://www.dyndns.org reliable for several dynamic IP addresses and it's a free service.
As I've set out earlier postings, password protection can be added...but only by running a webserver on another host in the LAN, with appropriate links to the NAS box.
The VPN would be the easiest/most secure.. DDWRT has a VPN option (and so do some brands of routers eg Draytek Vigors) but it depends on what DDWRT you have installed on your WRT54.
Yes, a VPN client is required ...freely available.