To be fair, once you get to those temps - most coaches will struggle!!
As Don mentioned, augmenting the Hurricane with additional heating sources, will be required. If the slides are not frozen, bringing them in for overnight, usually cooler, weather is one approach. Also when sleeping if you have two zones (Not sure if the 36' of that era does or not?). Closing the bedroom or bathroom door, and setting the front zone down to say 32, would let more heat be diverted to the rear. And one poster a few years back, said they used the Engine Loop all daylong, to build up a huge heat sink under their bed at night... Not sure if that's a good idea or not - but sharing...
Heated Tile Floors really help too. And when we boon docked on our Alaska trip in 6-15F for 9 days (Lake Muncho's Strawberry Flat Provincial Park.) we used a Mr Heater Heat Buddy (The large one, with the built in fan.) and placed that on the kitchen table. I'd get up and open the bedroom door, which by the way we were quite comfortable in with a few extra blankets, and our dog, in a one slide bedroom.) and brave the cold front room to start the Heat Buddy, then dive back under the covers to let the front heat up for about 20 mins on High. This would bring the temps up well, and I'd then brave my way out to start the coffee (Perculator with more heat via the Propane cook top.), and I'd set the Heat Buddy back to low setting, and that would keep us warm for about another hour or so.
Anytime we had the Generator On, we also would run two 1500W heaters, as well as we had Heated Tile Floors in the kitchen/bath areas, and the Electric Element of our HydroHot... We'd build up heat mass optimizing the diesel consumption. And we'd usually do this when cooking dinner (Solar kept our 800AH house bank topped off well.), so it was for cooking with the Convection Oven that we'd do this. Usually we'd run for at least an hour, sometimes a bit more, to get the coach up to temps.
At night, the rear zone was set to 38 (Which in our coach, was really more like 33) , and the 'rear zone' needed to be 'on' for the Wet Bay to trigger Hydro Hot on for heating. We'd be in the high 40's to low 50's with just our body heat in the bedroom, and I'd hear the Diesel fire up from time to time overnight.
We did have water freeze in the pipe run to our front kitchen the first night, but then I read from other CC owners, to leave the lower kitchen cabinets cracked, to let inside coach temperature penetrate into the cabinets outside coach wall, where the pipes plastic pipes where nested up against in our coach (2 Slide High Cascade, with Kitchen being Non Slide.).
On Mr Heater Heat Buddy, or other sources of Propane heat inside of of a coach. Do use proper procedures on venting the roof top, as well as window air flow. And we added two additional Carbon Monoxide Detectors, including one in the bedroom... This is a series safety consideration. We don't use our Heat Buddy very often now, but when we do, we feel we do it safely... so please do due diligence if you add an inside such propane heat source (Non venting to outside.).
And best of luck to you. -10F --- That's Martini weather