That budget would get you a pretty nice VW Dieselgate buyback Golf / Jetta / Passat. About the right size, the DSG is a lot better than a typical torque converter / planetary automatic, and definitely fits the mileage requirements. Plus, VW had to give these a pretty generous emissions warranty that covers pretty much the whole engine, and most of them in your price range will carry a CPO warranty too.
The Chevy Cruz looks like a fairly decent choice in that price / size range too, and you get a bit more car than most other brands due to typical GM depreciation. Or a Hyundai Elantra.
Accent and Rio both offered in hatchback through 2020, the Elantra GT (hatch through 2020) and the Forte5 was offered through 2018. All are good options for a Fiesta replacement.
I'll second the suggestion of a TDI as a newer car, a DSG Jetta Wagon diesel definitely falls in your price range, size and economy requirements. But be cautious, maintenance is only cheap if you do it yourself. 10k oil changes, 20k fuel filters and 40k DSG services costs will run expensive if you pay someone else to do it.
Might be able to get a final year Mazda5. Having owned a second gen fit, the 5 is like a bigger, vastly more comfortable Fit.
