I'm surprised that the AWD Pacifica is 150 pounds lighter than my Kia Sedona. To set it up for four down will run upwards of $2500. It would cost me over $3K to do the Sedona.
A few years back, U-Haul wouldn't do one-way rentals on tow dollies. Also, make sure that whatever dolly you get has brakes and can handle the Pacifica's curb weight and front axle weight. That Pacifica is too heavy to tow without brakes. Many rental dollies aren't fitted with brakes and are often limited to cars of 4000 pounds or less.
You'll probably be right at your hitch limit (assuming a typical 5000 pound hitch - maybe higher capacity on a DP), as a braked dolly that can handle that weight of car is going to be up around 850 pounds. I think your fuel consumption will be closer to 6.5 mpg with the car and dolly, if 8 mpg is typical running solo.
It sounds to me as though a one-way ticket on Allegiant to Bellingham then drive the Pacifica back to SoCal would be cheaper and quicker, but you don't get to have your living quarters and cooking facilities along or to do any sightseeing northbound. You also have to eat in restaurants and stay in motels headed south.
Having a car-carrier company haul it for you is probably the cheapest option of the lot.
A lot of variables to consider! Good luck.
Frank Damp, DW - Eileen
'02 Georgetown 325, F53, V-10, bought used in 2010 at 13,000 miles.
Dogs - 2 Labs again, both yellow males, both 9 yrs old and both adopted.
Beautiful drive, lots of places to stop for gas all along the 5. The grade at Southern Oregon is long and steep. Then you have Shasta area which is long and steep. They are both easy drives but you may not get your estimated MPG. That said, it is still a lovely trip. If you have a chance, Seven Feathers Casino has a very pleasant large easy pull through campground for an overnight and a nice buffet.