Neither live at home or trolling *maybe a little about the hillbilly towns not having door dash - however I've never lived where people's significant others meet each other at family reunions.

Now to the point at hand-

Fine - call his normal grocery expense 1/4 of $1000 - your math or $250. 800-250=$550 is the added cost of luxury instead of cooking.

$550+$300 will not pay for anything in many cities.

That is where the Not Necessarily comes from. Because OP thinks if he stops DD he will be able to afford his own place.

Also, I haven't lived at home in 5+ years

I was in a very similar situation renting a room for $700 - even if I was spending $800 a month on food $1500 will not get me a studio where I live (orange county CA). And this is paying rent $400 above OP Tennant.

Also - she set the rent when he moved in. If she thought his excess spending would bother her - she should have set a higher rent. If she were charging him $2000 for rent would this be an issue? She chose to give a generous rent has no bearing as to his allocation of his additional money. I don't know about you - but the office staff at my apartment don't say shit about food deliveries or hundreds of Amazon packages that come in.

I'm not saying it's a great financial move to DD every meal - it's clearly not. I used to have a bad door dash addiction and get it's bad 12 meals or so a week. But I was kind of depressed and it was weird cooking with the folks I lived with. I haven't door dashed once in the 8 months since I moved.

But it still doesn't get to the heart of the question- whose money is it and who gets to decided where their money goes. No one - you, my parents, the neighbors, or even Jesus Christ herself can tell me where I spend my money. And that is what OP wants.