Any deli's or small restaurants within walking distance of the Blackstone, to get food and bring back to hotel?
You have an amazing restaurant in your hotel, mercat
The concierge, front desk or bell service can direct you to numerous places.
There are also in walking distance a couple of grocery stores, Jewel and Trader Joe's.
Mercat is in your hotel and serves Tapas. The Artist's Cafe is just down Michigan Avenue and is (or used to be) a hang out for dancer's/musicians, etc. in the area. And, like Happi said, there are a few grocery stores within walking distance.