Commented and labelled disassembly: gist.github.com/1wErt3r/4048722
Decompilation project: github.com/MitchellSternke/SuperMarioBros-C. That project does not produce the ROM however, it reimplements an emulator + game in a single binary.
Video 1. Small Fire Mario glitch by Kosmic (2022) Source.
Video 2. Beating Super Mario Bros. as SLOWLY as Possible by Kosmic (2020) Source.