Save up or arrange financing and replace all of it. Hopefully you don’t have hidden rot elsewhere…

Yeah I don’t know a lot about electrical but I work in insurance and have seen quite a few “origin and cause” fire reports with pics of wiring that looks a bit like that. Sounds like you know what you’re doing 😊

Doubtful on the wallpaper but that original wiring worries me. Do you have plenty of smoke detectors?

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