The Enemies inside The Super duper mart doesnt respawn, they respawn at all other small/huge buildnings, camps , whatever, but just not there since its quest related maby.. i don't know ^^
Not true, I have been to the super-duper mart a few times after the mission and there has been raiders there, mind you that may have been weeks (in game weeks) after that mission, so maybe wait longer and see 🤔?