OK a lot of this is thinking...
Is DD OK, ask her, it's easy, doesn't everyone worry about their DC?
DH health issue, ask them, it's up to him to call the nurse to sort it, if he doesn't well he's gonna feel a bit grim a bit longer isn't he. Regards the job, again, ASK... The insurance, is he working away with no net access to sort it himself?
The refund, take a few seconds to check online banking.
The grass needs strimmed, right so do it? I could look out my window and think the fence needs painted, how's that stressful or a mental load. Oh look the sky is blue, that cat is white. You sound a bit dippy. Same goes for the key and the plug, just go get it cut then?
You don't have to feed guests, you're not responsible for catering to guests particularly those you haven't invited yourself, if whoever invites them wants them to stay for dinner or whatever that's their problem to sort not yours.
I think about stuff all day, don't most people, is it really stressful? Am I doing it wrong?