I wouldn't buy a higher mile gen1 ecoboost, and this is coming from an EB lover. Too many issues with the first gens. 2nd gen FTW
For $20k i'd get an 11-14 5.0 crew cab f150. Forget getting 23mpg. If you have a weekend car and only want to spend $20k on a crew cab truck that can tow, you're not getting 23mpg nor do you need to. 18mpg vs 23mpg probably comes out to $30-40/month in fuel so it's probably not a deal breaker.
Your budget has to go up or your towing and fuel economy expectations need to go down. If the budget goes up, 2.7 ecoboost all day.
FWIW after 5k miles in my 2018 crew cab f150 i'm getting 21.4 mpg average, mixed driving. 3.5EB and 10 speed