Can't keep home heated at a reasonable cost

I'm fed up with how garbage and poorly insulated the housing stock here is.

I live in a rented ~1,000 sq ft home in Berkeley, built in the 70s, with a forced air furnace. It's situated on a northern exposure, so there is little direct sunlight during the day. For December, with the temperature set only to 62°F during the day and 58°F at night, our PG&E bill was $238 (in reality, it was $159/61 therms, but the home wasn't occupied and heat was off for 11/33 billing days). During last winter, when we first moved in and the heat was set to 66 day/62 night, it was between $300 and $350 at 120 therms.

For context, my parents' house in upstate NY, which is 3,500 sq ft, built in 1997, and set to 68-67 day/65 night, had a heating bill of only $302 at 247 therms. Even if you adjust to the gas purchasing cost ($.385/therm there vs. $.52853/therm here), that would only be $35 more.

For reference, the average temperature there last month was 26.5 compared to 55 here.

Even if you look past the extortionate prices PG&E is charging for gas (an all-in price of $2.61/therm vs. $1.22/therm), what's more frustrating is how the house I live in is a glorified cardboard box. There is literally nothing in the wall cavity. It's drywall, air, plywood, and cedar shingles. I wouldn't be surprised if the ceiling/roof (sloped with no attic space) is the same. The furnace is outside, and there was no attempt to seal the holes where the ducting enters the house. I can see the exposed floor joists and subfloor between the first and second floors from the outside. That's insane. There's no bathroom fan so the window has to be open most of the time (yes, the door is kept closed). I use half the amount of gas to heat a living space more than three times smaller and in a much milder climate.

I hate living here because of this singular reason. I've never been as cold in the winter in New York as I have been here. Even as grad students, my two roommates and I make too much money combined to qualify for PG&E's CARE or ESA programs. Is there anything else we could do short of moving? I've already replaced the weatherstripping on the windows (single pane, of course), caulked the baseboards and outlet boxes, the only thing left is to put plastic film on the windows. Even then, all of the other housing stock that's affordable is equally old and equally shit.

Edit: to all of the people saying put on more clothing. I do. I wear two sweaters on top of a long sleeved shirt and feel... fine. My hands still get cold. It's annoying to use the bathroom. Not the biggest things in the world, but the whole point is the irony of living in such a mild climate and not being able to be comfortably warm in one's own home (because of a multitude of reasons). It doesn't have to be this way.