If you're seeing the firewall icon, chances are that other users can't download from you (so you see no uploads). In LW go tools > options > bug reports > view example. Scroll down to 'recieved incoming this session'...if it's false, you can't recieve incoming connections from other computers.

I can't find anything about TT&T that's in English...so it's a bit hard to say whether they're definitely throttling bandwidth. It sounds like it though, a lot of ISPs do it. If your connection status improves during off peak times, try downloading at all different times...maybe your speed will jump up a bit then as well.
Try downloading a file from here & see what speed you get
http://www.magnetmix.com/video.shtml

Something you could try is changing ports. In LW go tools > options > advanced > firewall config. Now change LW's listening port to 64049 (or something in the range of 49152 - 65535). Apply > ok. If you do get port forwarding up & running, the port forwarded & LW's listening port must be the same number.

You're router's a toughie. It does have a firewall but like you said, there's not much documentation! Have a look here, see if you can find any good info about port forwarding.
http://www.paradigm.com.tw/Support_ts.html

And sorry, this page doesn't translate but if you can read it...
http://www.thaiddns.com/webboard/mes...ly.asp?tid=747

It wouldn't hurt to update your Java. Use the JRE offline installer here & remove your current Java before you install the new version
http://java.sun.com/javase/downloads/index_jdk5.jsp