Regarding the tips, the default on Instacart is 5%. I tried raising to 20% to see if it would get me a delivery slot, and it doesn't.

I'll kick it up to 10%, now that I think about it. I see that you can pay $9.99/month to avoid delivery fees (which are separate from tips), which looks like I should probably do.

I think I'll try late at night. If it fails, I'l have to move to plan B and start talking to people I know in the community who might like the job of delivering groceries to me.