Insulation Questions

Hi everyone,
I'm new to operating a wood insert. We just moved into a 3300 sq ft house built in 2005 and purchased a Hampton HI300. We love the look of the unit and it blows a lot of hot air. The issue we are having is the house does not heat up. I knew it would struggle to heat the entire house, but I hoped it would keep the living room where the stove resides warm. Even with the bedroooms doors shut, the room with the insert is 63 degrees when it is in the teens outside, 66 degrees when it is 25 degrees outside (right now). When the temperature outside rises into the mid 30's the room will get to 70. When it gets to into the 40's, the room finally hits 75. The house has a center hall and the upstairs hallway is usually the same temperature as the downstiars room with the stove, so a lot of the heat is making its way up the center hall.
My question is: Is it normal for the inside temperature to fluctuate so much based on the outside temperature? There are a lot of big windows and a slider in the room as well. I purchased blids for the windows. My brother-in-law suggested we stuff fire proof insulation behind the stove.
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I am not expecting to heat the entire house, but I was expecting to keep the thermostat set at 60 for the rest of the house and keep the room with the stove in the 70's even when the outside temperature drops into the sigle digits. It this too much to expect? Is it worth insultating behind the stove? We are planning on purchasing blinds for the slider, are there any other suggestions for keeping the inside temperature consistent regardless of outside temp?
Thank you for any help.
Andrew

Thank you for helping me work through this. The stove was installed by a reputable dealer so I assume it was done properly. I will verify this weekend. Ceilings are 9 feet. I am keeping the ceiling fan off because I do not want to push the hot air out of the living room. The house was built in 2005 and the quality of construction seems to be high. I do not feel drafts around the windows, but it I do detect a colder temperature in front of the slider. I am uploading a picture where you can see the slider, 2 small windows, and 2 36X62 windows. There is a similar window to the left of the fireplace and 3 more in the kitchen area. The slider and kitchen windows have no blinds. The fireplace is masonary / brick. I know heat is entering the room because the ceiling fan is slowly turning when the stove gets hot.

Picture of room and stove.

The enamel does not reflect the flash very well.

From my understanding, ZC refers to materials other than Brick or Stone. I can confirm that behind the fireplace on the outside of the house going up to the roof is brick on the 3 exposed sides and I assume brick on the inside (Against the house). It could be I don't fully understand what ZC means. I will get behind the stove and insulate this weekend. How much more heat can I expect? Would heat loss from the back be significant? I do have a blower and it is surely blowing hot air into the room as the ceiling fan begins to turn on its own.

Thanks to All. I am already learning a lot form this site... Torus and ZC. Fan is now set to clockwise and on slow. I felt a breeze on Med so I assume that is too fast. My wife is in charge of curtains and the fashion decision hasn't been made. Blinds are all I am allowed for now.

The fan in the living room is now on. I didn't notice much difference either way. Here is a picture of the outside Chimney. 30 feet of brick.

It looks like there isn't much else behind there but the pipe. I'll be getting fireproof insulation back there and the block plate. Also, I wish I had looked into the actual space instead of relying on the dealer because I would have gone with a bigger fire box. Hopefully the insulation and block plate will be enough.