Well Zippy,
Sounds like a nice trip to me. You did not say what your RV was and how fast you normally drive. I made a similar drive this summer and followed you going route back from Seattle. 1. Yellowstone is "BIG" we stayed at Flagg Ranch just south of the South Entrance and were happy with the location and the hook ups. It is convenient to make daily trips into Yellowstone and into Grand Teton. You need to get up early see the animals and to beat the traffic. Most people stay in bed until mid morning and drive slowly through the park. When you leave, the road through the Park will take you through West Yellowstone and north to Shelby on I-15 and then west to Glacier. We stayed in Cut Bank near East Glacier, which is less commercial than West Glacier and were able to see Two Medicine lake as well as riding the park shuttle across the Road to the Sun to the West entrance. There is also an interesting Blackfoot Museum at Browning. Our crossing into Canada on I-15 was uneventful. Check passport and questions as to if we were bring firearms or alcohol. On your way back, you might want to consider seeing Little Bighorn, Mt Rushmore area. There is a great county park Hardin, Montana and be sure to visit Pompey's Pillar on I-94 just east of Billings.
As to driving time and distance, on the days we drove, we would be on the road early 8 AM and planned to stop by 3:PM. Most of the "Sightseeing" type tourist stops along the way didn't open until 9AM and the stops were 1 to 2 hours at most. We planned our two night stops around the larger attractions. Some days we only drove 150 miles, other days we were able to make 300. I pulled a 25 foot 5th wheel and at 55 to 60 MPH. It seemed to average out with rest and fuel stops at about 50 MPH.
There is a lot to see on your trip and you might as well take your time and see as much of the land as you can. There are a lot of hidden "Gems" along the way and you may never have the chance to go back.