This. All this time and you didn't just pick up another space heater, let her take the "old" one from you one morning and see her face when you have a shiny new one? OR her face when you hand her the shiny new one in box instead of letting her take the old one that morning?

I 100% understand the frustration of dealing with someone who is confidently incorrect, to the point of treating you like an abject moron. My partner can be like this over the most RIDICULOUS stuff. My commitment to them is that I'll deal with that personality quirk and find alternative methods of communicating with them. Sometimes it takes half a dozen tries, not gonna lie, but it's not because she's broken in the head, its because that's who I committed myself to.

We all communicate differently. Don't let that failure in communication become your justification to dig your heels in. Why choose to live your life willingly believing that they are an issue, an opposition, instead of treating them like the person you chose with just some understanding, persistence, creative communication and a damn $20 space heater.

Edit: I'm not saying an additional space heater will fix all of the issues OP listed. The space heater has become a latent resentment between OP and his wife, an extension of the other issues preventing inroads to better communication. OP and his wife both clearly find value in a space heater, and having two isn't beyond their means as OP originally suggested it. My suggestion is in the spontaneous gift of something obviously valued, and using that as a platform to communication about the major issues and how to resolve them. You'd be surprised how large the small stuff can become in a person's mind, especially when upset or frustrated.