For type 2 diabetics some of the new inhaled insulin products like Afrezza seem to be more forgiving of temperature fluctuations. These appear to only be the fast acting insulin's so not a big help for the type 1 who also needs long acting insulin.
There are no products that I am aware designed specifically to keep something just above freezing without going over 70 (or lower degrees).
I travel with a type 1 diabetic, and I have spent several years living off grid, I am not a Doctor, and the following are just suggestions, you will want to run any potential solution past your medical provider.
Your first point is keeping a 90 day supply at refrigerator temp. As we know a 90 day supply through many insurance programs is cheaper. A 30 day supply or 28 day according to this source can stay at room temperature. So changing your refill quantity could make things easier, allowing for a larger range of temperatures.
If you are totally off grid but able to maintain a room above freezing products like the frio can really help with temperature stabilization. We own several of them in different sizes, and they have really helped us be more mobile.
Keeping dependable refrigerator temps off grid, is really hard. There are 12 volt and propane refrigerators, but in my experience, the temperature control is not fine enough to risk insulin in. A couple of ice particles in your beverage is fine, but in your insulin, could mean your death. If your going to use a refrigerator to cool insulin in a warm room, I strongly suggest only using a 110 volt unit (not a dual or three way model, a 110 only household model). Which means a very expensive off grid power supply, that provides juice 24/7.
Keeping a room warm is not difficult, if you are there. But the most cost effective solutions are wood and Kerosene, for the very budget aware solutions these are going to need attention every 8 to 12 hours at the outside. If you are gone for 24 hours, during an arctic winter day/night the risk of indoor freezing temps is very high.
If you need to keep heat going while you are gone for say a 72 hour round trip into town to pick up meds and supplies, and you are totally off grid, a propane heating system is probably the most cost effective solution. Our newer camp trailer has a thermostat controlled propane heater, that uses a 12 volt power supply. How much battery and propane you need depends on the size area you are heating and how much insulation you have. My off grid time was in Washington state, and I found a 100 pound (25 gallon) propane tank was large enough to last several days, even with the heaviest usage, and small enough that I could move it reasonably well.
In summary; If I was going off grid, arctic winter, with type 1 diabetic supplies. I would get insulin refills every 30 days, use a frio to keep the temperature stable (also helps keep the chill off for short periods). I would use a thermostatic controlled propane heater with a 12 volt fan. I would have at least two 25 gallon propane tanks, and head into town for more propane no later then the day I connected the last tank (sooner is ok, but make sure you have a full tank connected the day you leave). There are a lot of variables on 12 volt usage, so you will need to figure out how many deep cycle batteries you will need to keep the house going for 3 days. Keep in mind, a snow covered solar panel on a cloudy day is not going to provide any energy.
Additional Comment Currently we travel with a camp trailer, that has a 110 and propane power options. We never put insulin it! We do use it to freeze, freezer packs, which we then use to keep the insulin (and other meds) cool in a small cooler.