1. Downloads usually go backwards due to file corruption. Initially LW downloads the Hash of the file. Then at end or/& during download process it rechecks the hash compared to what has downloaded. If any parts are missing or different (possibly corrupted) then LW will attempt to redownload those parts. From memory LW attempts to do this up to 6 times before giving up. You will see this happen out of mystery due to you having previously received a corrupt file message & you chose continue download & ticked the option to 'always use this answer'. Thus you will not be warned of this happening again.

Chances are the part(s) (bits or bytes) of the file that it is attempting to redownload are not a major corruption or change. I've had this same issue with video. And chances are the file is already 100% downloaded. I launched the incomplete video from Library window & found all was good. I copied the incomplete file to my download folder. Then continued the download until it eventually finished. Both were the same. So I'd suggest you try the same by launching the incomplete file. If it is good, then cancel from download window & move the incomplete to your download folder. Rename it to how it should be.

2. Some of those in your upload window will be people downloading the Hash of the file so will finish very quickly.

Transfer interrupted is probably not unusual for dial up since most people will have problems maintaining connection to your dial up connection.

Queued uploads is also not unusual for dial up. Either not enough bandwidth or upload slots available for them to download from you so they are in a queue waiting for an upload slot.

Upload limit reached, I'm not sure but similar to the reasons for Queued status; your upload slots or bandwith set to be available for uploads have been reached/peaked.

Gnutella network works in strange ways at times. Suddenly a certain file desired by many and they are directed to your LW. Keep in mind uploads may be a part of partial file sharing. Both your partial files and others, so they are downloading from both you and others. And whilst you are downloading a file, they may be downloading as much from you as they can at same time.