2019 radrover here. In my measured opinion (measured with voltmeter), the bar display on the radrover is an optimistic lying dog. My daily commute is 10 miles roundtrip with one 400 foot climb&descent each way, PAS 3 the whole way, maybe 10 stops forced from lights.
I know the bike is good for max 35 miles on PAS 3, with the last 3-5 miles being on lower wattage than I'd like. Yet, after my first completed 10 mile day, the bar meter reverts to 100% as soon as I stop drawing power. Now, I know this is bullshit, because I've just used up the best (highest voltage) 29% of the range. After the 2nd 10 miles (for 20 miles total), I sometimes see 80% charge on the bar meter, even though I know I'm touching the last third of the range. Mind you, I'm measuring 47.5 to 48.1 volts on the battery after the 2nd ride. Meanwhile I know from experience that when the bar meter shows a steady 40% I'd better be within 5 miles of home or car.
Getting 36 miles on PAS 3 with more hills than me will likely be a stretch. Stop using higher PAS on climbs, or sub in PAS2 at 1/6th power (yes, that's how they programmed it) on some of the flats. It is at least a good workout. Also, ride the bike without power for a couple miles (you can put it on PAS0) so you'll know what to expect if/when you run out of juice. Then try to stretch to two 18 mile round trips on one charge.