Phaedra is it possible to maybe try the online shopping, both try working it out together then hopefully try encourage him to slowly take over the online food order, maybe try leaving the car sometimes and take a taxi to shorter destinations if out and about, accounts were/ think still available so possibly he could get used to that sort of thing for appointments etc..
It is a worry for any parent to what will they do when I’m gone and would understandably be added concern due to your sons autism, one thing for sure what a great Dad he has in you..