Phaneron

Answer: They were actually planning on using Jigsaw as the villain in the sequel until Thomas Jane and director Jonathan Hensleigh exited the project and the studio rebooted the character with Punisher: War Zone. They probably just wanted to show the Punisher's origin first, which would allow him to be fully established by the time a sequel came around, and they would have more to screen time to establish Jigsaw.

Phaneron ★

Answer: I'm just guessing here, but since dozens of people were killed in what was determined to be a mob hit, and since there were no next of kin, everything was probably left there and boarded up since the entire area was a crime scene that was still under investigation.

Phaneron ★

Answer: Jimmy is drowning in massive gambling debt and has had to resort to selling everything of value he owns as well as steal money from evidence lockers to help pay his debt down. He has nothing to live for and is merely going through the motions of life, and coupled with his guilt over selling out Frank and getting his family killed, Frank concludes Jimmy needs to take his fate in his own hands.

Phaneron ★