Calibrating white and black points

[Ofnuts]

The fact that Gimp and Adobe don't agree on the colorspace is suspicious. Gimp uses sRGB unless told otherwise.

In Curves and Levels you can set the response on each color channel (Channel selector at top left under the Presets).

Did you try Gimp's color management (a whole raft of options in Edit ➤ Preferences ➤ Color management)