Did my longest roadtrip so far with my Prius PHV- around 1200 miles during one week. In Finland now we have extraordinary warm summer - temperatures during the ride have been more than 82 F constantly. My trip had a lot of motorways +300 miles, when I was driving 75-80 miles/hour. One longer journey without motorway was 180 miles. Also drove around 150 miles in cities. Did not hypermile, used A/C as in any car, car was fully packed and had 3 - 4 persons. Also did not use any extra time in any journeys for charging. Just normal breaks with the kids. I charged car 7 times from zero and 4 times around half. (During the longer journeys or in the middle of the day). My avarage consumption was 65 MPG. During that 180 miles journey without motorway it was 82 MPG. So did enjoy the ride and I think this is one of the only cars where you can get this kind of figures in normal driving .
Yes now the public charging network starts to be pretty good. Especially for road trips it has been been building rapidly during last 12 month. I hope that Toyota would introduce rapid charging to Prius PHV in other countries than Japan - there it is already installed
So your got 65MPG with charging 7+4x0.5=9 times, with approximately close to 300 EV miles, and used 18.5 gallon of gas. So your gas milage is around 49mpg. That is not bad.
The slam dunk thing I liked and miss the most about my Prius, was IMO it's the absolutely best long road trip vehicle you can have. Chosen destinations from point A to B were only really evaluated in terms of chronological free time to do them, and the cost of everything BUT gasoline. I was always impressed with how far I could go, on so little fuel. Which made long road trips that much more enjoyable.