You could wait for the diesel version of the Ram Promaster, but I suspect that engine will not be made available for the smallest van, so you might be looking at 4 or 5 rows of seats. MPG will not be as good as Euro models of the Ducato (and competive brands we don't get), which get by with yet smaller turbodiesel engines (and six-speed manual transmissions in some cases) but do not meet performance and frills expectations for U.S. market.
My choice in North America would be the Traverse, though it does not get as good MPG as the Honda, and third row accessiblity is not up to par with Japanese and Korean brands still configured as minivans.
Smallest thing sold here with three rows is the Mazda 5, but U.S. safety standards reduce seating from 7 to 6, and MPG is not that much better than a new minivan or 4-cylinder version of "compact" SUV like Escape, Equinox, or Calibre.
Nothing new is going to meet your price expectations, car prices have almost doubled in the last ten years. Try shopping 3-5 years old, about 50,000 miles used, for prices that leave room in $30K to also buy a trailer. But as little as you plan to use the RV, you might consider a 10-20 year old motorhome, and not worry about MPG on those trips, because nothing really gives good mileage towing a box with 65-90 sq ft frontal area, no matter how well it might do in daily driving.
E.G. my daily driver (actually used more like 2-3 trips a week) is a 35 mpg subcompact MPV, RV is a 7.5 mpg sel-propelled house that can tow the daily driver.
Tom Test
Itasca Spirit 29B