Welcome Epoch (nice clear posts)

First, update to the latest LW (4.0.4 today)

Re 1, Just click the force IP checkbox. The other box is only for alternate ports. Your Public IP is retrieved automatically from responses received from other connections. Yes, it's not entirely necessary as the push will attempt to work around the problem, but if you can eliminate the need for the push, your connections will be better.

2 Once you can accept incoming connections you have the maximum chance of getting the fastest download speeds. However, speeds are then dependent on the host(s) serving the file. If they are uploading to many clients, their speed is distributed amongst all, and if they have a slow connection, you can see why they will serve the file even slower. That is why finding a file with many sources is best: LW will automatically choose the fastest. Typically most home users don't have the bandwidth commercial sites on the Internet offer. Comparing the two just aint reliable. You're right about the info in the download thread--it's pretty dated and many of the suggestions no longer apply. With most prefs to left at default, I can regulary get 200-350 KB/s download speeds (my max is 5mbps) by downloading from multiple sources after a quite specific search and repeating the search after 15 mins or so.

3. Sources may be around but busy, or have gone offline. I'm not sure how long search results last after the host goes offline or since changes with a dynamic IP

4. Gnutella has a rep for music files, but I find lots of video. Just depends on what others choose to share.

Cheers