Hello Rabbi Michi, for reference: Does a person who violates Shabbat, who is faithful to kashrut, make sure not to cook on Shabbat? I would appreciate the source and reasoning.

I have no source and do not need a source. Testimony in prohibitions is not testimony but evidence. Now go out and consider whether there is evidence here or not. This is not a question of halachic sources but of assessing reality.