everything can be removed by patience and proper tools.
First, I would score the edges where the metal meets the walls. This will score the caulking and paint build up so that the removal will not tear or ruin the walls.
Then I would carefully with the assistance of a wood chisle start prying away the metal frame.
Make sure that there are not any screws, nails or other fasteners that you could remove to make the process easier.
Later, you might want to use that new pry bar to assist you. Place a piece of 1x on the wall so that the pry bar will not indent the walls.
It will come off, you just need to be careful.
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