One of the paths I took to get into
permaculture was through the survival community, and I hit this question too, looking at it from an emergency type situation point of view. I came up with several answers, and you might find some of them interesting.
Looking this from a
Wheaton Eco Scale point of view, there are many levels of answers to the question of using oils to light your home. The question "how safe is it to burn crisco in the house" is not a zero level question, because you obviously have thought about the potential toxins, and the problems with the petroleum companies and all that. The really interesting answers are what are the answers to the question that are a few levels above this?
Permaculture and Permies.com are focused on finding positive solutions to a problem by looking at it from a different perspective, and coming up with long term answers that just sidestep the toxic answers altogether. When you know what the answers might be a few levels up, you can move toward that solution. So starting from the lower levels, going up toward higher level solutions, my answers to your question::
I'm going to ignore the GMO part of it, since that is classified as Cider Press territory here, and not up for discussion in the main forums. The part that I don't like about Crisco and cheap veg oils is all the chemicals they are grown with. What do they do when burned? No one can really
answer that one, as far as I can tell. Best answer is "nothing good for you to breathe." How much is too much? No one can answer that one either, as a lot of the body damage is long term cumulative damage, and there are few good studies on it, due to the complexity. Is it safe? My first level of answer is no. An unknown dose of a cumulative toxin can't be a good thing. All the essential oils in the world can't detox it. But there are ways to make it safer, if you absolutely must do it, if you have a bunch of Crisco around already, or it's an emergency.
My next level of answer is vent it safely. In an emergency or very low budget solution, an oil lamp chimney that is lifted up slightly on something to let air get under it (like chopsticks, maybe?) that has a tinfoil chimney pipe made that vents out a window or crack. So the light comes out, but the fumes are removed from the house. If it's being done long term, and the heat is wanted too, a better pipe and some thermal mass around it, kind of a low end
rocket mass heater. There is a thing that runs around the net, using terracotta pots as thermal mass around a candle, like that, only with the glass chimney involved to let the light out. And I hear you say "this is getting silly, too much work for this" and you are right. Duct tape solutions on a badly designed system will just get more complex.
My next level of answer is related to the soy candles comment. What I did when I was asking this question was buy organic soy wax and pour a bunch of candles into mason jars. The lids keep the candles dry, so they can be stored and used in an emergency.
My next level of answer is related to the vegetable oils comment. Ah, this is where it gets interesting! Yes, vegetable oil burns well, has been used for millennia for light. If you are looking at the cheap stuff from the grocery store, I
class it with the Crisco: toxic fumes, vent it if you absolutely must burn it. Organic oils are nontoxic and will burn nicely. And this is where we start looking into
permaculture oriented solutions. Why give
any money to people whose business practices you call shady? Lots of plants make oils that can burn, something oily will grow in any climate, a lot of them perennials. Look up "oil seeds" on the forums for more info on what might grow in your climate. (I see you are north, or plan to be north, I am not up on what you can grow there, I'm up on southern crops.)
And
bees make wax. I see you have posted on a bee
thread, so you are looking at them, and know the long term usefulness of
bees. If you don't have bees yet, buying bee wax is more effective price-wise than cheap oils, as it burns slower. Buy it unrefined, and melt and clean it yourself and it's not extremely expensive. If you buy beeswax candles at a health food store, yeah, they won't be cheap. They
will burn longer than the same volume of vegetable oil though.
How can you get beeswax cheap? By having your own hives. But if you have no
land yet? How about finding places someone will let you (or even pay you!) to put hives on it and maintain the bees? Plus honey to eat and
sell! Now we are function stacking, turning a problem into
profit!
How's that for weird answers to your question? :) Things to think on, ideas to work toward, that are nontoxic long term solutions. That is what
permaculture is about, sidestepping the toxic gick by reframing the question and looking for different solutions than the shady companies are offering us.
Looks like you have been on this forum for a month, Welcome to Permies! Come down the rabbit holes with us and learn stuff, it's great fun! :)