IIRC, your landlord installed “You might as well set dollar bills on fire” resistive heat.
To stay comfy and warm at night, Heated Mattress Pad FTW. I’d say that with cozy blankets, you could do 60–62 easily at night, though you’ll hate getting out of bed!
I will say that as an added bonus with resistive heat, you don’t have to feel the least bit guilty about using Halogen and incandescent bulbs, no efficiency loss at all if you have to burn electricity for heat anyway; might as well get some light out of the bargain.
At what temp will pipes freeze? Depends on where the pipes are located, and how well insulated the place is. Pipes running through an exterior wall that’s uninsulated will freeze at pretty high temps. Pipes running only through interior walls will never freeze unless the temperature of the apartment actually goes that low.
Barring uninsulated exterior walls, I don’t think you’d have to worry at any temperature you could tolerate living in.