This was our first trip to DLR and our first Halloween Party, so I may not be the best person to answer your questions, but I'll give it a shot.
- Ride lines were long when we got there at 5:00. By 7:00 though when fast passes were done and non-party people had left, I thought all the lines were short to reasonable. Most seemed to be in the 5-10 range. We waited 20 for Star Tours right about 7:00, but I think it got shorter after that. At one point, I saw Space had a 5 minute wait. Splash was walk-on to five. We waited 15 for Astro-Orbiter right around 7, but it was 5 later in the night. Pooh was walk-on. Haunted Mansion was the only thing that seemed to keep its wait time constant all evening. It seemed to range from about 25-35. Maybe it went down after fireworks? We left then.
- Haunted Mansion 25+, Space was over an hour when we arrived at 5, but dropped quickly after 7:00 to 5-15.
- Can't help you on fireworks. We weren't paying attention to the time and were on Splash when the fireworks started! Oops!
- Villian lines were awful, at least to me. It wrapped around to the front of the park. Captain America was about 5 minutes. Pooh characters were about 10 minutes. The line looked really long for Jack Skellington. We missed out on the Toon Town pre-party, but it sounds like that was a disaster. Tremaines were just choosing people for pictures. There wasn't a line.
- I would not call any of the treat trails "well done". They were just taped lines on the ground with carts handing out candy. I did not see any that were at all decorated beyond the balloon and/or sign at the beginning and end. Maybe I missed out on "well done" ones? The line at the one in Tomorrowland was ridiculous. In hindsight, we shouldn't have waited in that line. It wound around and around forever. The lines in Critter Country and New Orleans Square were much shorter.
Overall, we had fun, but I'm not sure I would do it again. I'm glad to have done it once. Although, if I did it again, I would do some things differently. I would ignore any treat trails with long lines. You can find ones with short lines. I would more carefully plan when/where to find the characters I really want to see. The lines are just too long to see them all... you have to prioritize.
I liked that the ride lines were short, but everything else seemed so crowded. I think there were fewer people on rides, but so many more people wandering the streets going to see characters, going trick-or-treating, etc. It just seemed sort of mobbed with people, and some of the character lines were not worth it to me to wait in.