New member please help now!

Sounds like poor insulation. I can keep nearly 2000 sq ft at 70 degrees on level 3.

Its your house. That stove looses most of it efficiency much past a setting of three let alone 5. You need more horses to heat that much cave.

3500 sq. ft. is a lot of area to heat when it is broken up
by hall ways, door ways and different levels.
Remember a pellet stove is a space heater no a central
heating system . Yes some people with open concept houses
heat them with a single stove. I am not able to heat my well insulated
150 year old log farm home with one stove (2200 sq. ft.) to many levels
turns and twists . You may be able to heat with 2 stoves depending on the lay out

You have a far less than ideal setting for a pellet stove, unless you plan to live in only a portion of that house in the winter. You note that you can't afford oil, but you have new windows, etc. And you're considering the purchase of a new stove that is a few thousand dollars... I suggest that you may need to think this through a bit more. In general, your money is best spent first on adequate air sealing (caulk and foam and such to stop high rates of air exchanges), then on insulation, and then on your heat source. You likely don't have an outside air kit (OAK) on your stove, which is bringing in cold air. And unless that's a small stove and/or a big room, most stoves would be able to heat it to well over 72 if desired, at a higher feed rate. This suggests the stove is not performing well and likely needs cleaning/maintenance.

You have factors that need to be addressed before buying another stove. I suggest tackling those first. Perhaps an energy audit by a BPI or RESNET certified energy auditor would be a first step. Google away for those in your area, Expect to spend about $500-700 for that, and don't rely on the audits offered for free unless sponsored by your utility company (the free ones are just sales pitches).

I agree fully with what others above have stated. I assume you have high ceilings also given the type and age of the home. You really need to work on the air leaks, insulation, and homes envelope first. Then as Bioburner said and again I agree that you need more stove and BTU horse power. That is a lot of area and distance to heat. Being a cut up and compartmentalized floor plan is not doing you any favors either. What square footage and BTU rating is your stove? Do you have access to wood? Wood burners are a lot of work but can be found for cheap compared to the prices of a pellet stove to help get you by. Just another option.

The Mt Vernons are good units but that comes with a price tag like many others. Step back and access what you have to deal with. Throwing band aids at something that needs stitches is going to put your farther into the money hole. What can you do to improve the homes insulation and sealing it up better? The price of another pellet stove could go a long way used to tighten your home and insulate better especially with your sweat equity or doing so yourself. I am running a stove that's 68,000 BTU's to do two levels at 2,350 SQ FT. It has an open plan and does it well but my perimeter is tight although I have tons of windows and glass doors with mostly (over half) vaulted ceilings. Many heat entire homes to a reasonable comfort level all winter long in very cold areas with a pellet stove or two but have taken first steps first. I have more than the 2,350 SQ FT to do and I am now looking at adding another stove to increase my BTU horses and do another area and to supplement the far reaches of my current stove. Remember the farther you get from the stove the cooler and harder to heat it is. Anything can be done and remedied if you put in the effort.

Not trying to discourage you here but being realistic. Many here have been in your exact shoes and have decades of wisdom on this matter. Many have learned the hard way. Best of Luck and we will be happy to help. Around here we do not like cold people and houses. We also do not like others spending money without good results. I am always looking for ways to improve. My wife HATES the cold and believe me I hear about it frequently. She is much happier now so I have my ammo to tell her to pipe it down when I drag this other stove home hopefully tomorrow. Bet she is happy about it even. She was a little miffed when I spent a lot of cash on one a month ago. It's all good now since she is comfy!

Sounds like a drafty barn (size wise) your trying to heat. Not my realm, but maybe a pellet or wood boiler system plumbed in to the existing heat system? That and seal it all up. Your energy company should provide this service and a near free inspection of the homes efficiency (or lack thereof).

I have a pellet stove that puts out a little more than 48,000 BTU heating a little less than 1400 square foot. When the outside temperature dropped into the teens earlier this week it took everything the stove had to keep the room it is in at a comfortable temperature. This was on it's highest setting, it was clean, it was properly adjusted and burning the best pellets I've been able to find.
A similar size wood stove will cost less and should be able to melt the stickers off your new windows while burning crap wood.