Using a tent to trap warmth is such a good idea. But make sure you’ve got a good mattress/pad that will insulate you from the floor. I lived in a camper trailer without utilities in Michigan for about 5 years and even though I am a quilter, own tons of quilts, they were never my only blankets in the winter, usually one or two combined with sleeping bags/ duvet. I second everyone saying a sleeping bag is the way to go. Any way to create and trap a hot pocket around you including head/ feet. I used to blanket off my bed area because even that would trap a small amount of body heat in the air around me. And when you get out of bed for anything don’t flip the blankets off you and let out your hard earned heat! Slip out carefully so the heat stays in.

But my secret and best weapon against freezing nights is my 80 lb dog curled under the blankets, seriously makes a huge difference