I agree that memory is likely stored in brain and doesn't stick around after the brain shuts off. Sleep is similarly scary. Though memories can likely be downloaded and saved somewhere.

Yeah, it is indeed very hard to know if anything else is concious with certainty. I would say that it seems like a safe assumption though to assume other humans are concious, animals too, particularly mammals. It is entirely possible atoms in general are consious but seems less of a safe assumption.

Regarding the integrated theory.. if you cut out someone's eyes or sever their spinal cord or directly cut out that chunk of the brain, maybe they lose a part of their concious experience but it's not like they stop being consious. There still seems to be some core somewhere there that integrates the rest together.