It wasn't a dumb idea, I think it's just the way I said it and didn't explain everything. I'll redo it.
Jill was there before Leon and Claire. Brad died and she found Marvin only unconcious because he got bit, and Leon and Claire found Brad's zombie and Marvin turned into a zombie. The ladder is up probably because during Outbreak, maybe to stop zombies after Kevin went outside, somebody took the ladder up (only thing that makes sense, really), and probably in between cutscenes and gameplay Marvin, Kevin, and other people boarded up the doors. The statues are unexplained.