Some answers:
1: If you go to your webaccess tab in the linkstation configuration tab there is a setting for how long a person using webaccess can stay on, I think its called Session Period, it might be set to a small amount of time.
2. The torrent system on the LS never worked for me, as far as only being able to view part of the file, as far as I know you usually have to wait for the file to be downloaded completely before you can view it. Is it done downloading? Could this be your problem. Remember a torrent downloads in little bits and pieces, so even a file with say 10 pictures, it will download portions of those 10 pictures at a time. Not one picture then the other and so one. So maybe you need to wait till its all done.
3. As far as the port thing, the other poster is correct. Forward what ever port you are going to use to the ip address of the LS. Its a bit more complicated than that because some ports wont open even if you forward them, also when you are accesing the LS away from home you will need to enter your WAN ip not your local ip. So something like 24.45.789.161, not 192.168.1.xx. Hope this helps.