Can I cook with the olive oil from canned sardines?

Yes, you can use the oil for other purposes, although due to the strong fish aroma and taste it would probably best be used only in a fish dish. I frequently use the oil from anchovies to fry onions to add to a Bolognese sauce to add a depth of flavour, a few anchovies being frequently added to this dish as "Italian MSG". It also works well added to tomato sauce for pizza toppings.

I would use the oil to fry onions and garlic for say, a fish casserole or stew. I would add some additional olive oil as well though, as the smoke point may be affected by the soluble fish oil already in the product.

Fish is a very strong aroma as you say, so you have to be careful what you use it in as it will overpower and dominate. Although I have not tried it, it may also work well as a replacement for fish sauce in some Thai dishes.

That sardine oil is going to be primarily useful for dishes that already have a strong fish flavor -- such as from the sardines themselves. For example, multiple recipes for Pasta con le Sarde include using some of the oil to cook the pasta sauce, which also includes the fish.

It's notable, though, that many recipes do not use the oil from the can. Even in a dish that includes the sardines, that oil can be just too fishy (that's my own experience).

It would also be interesting to try using the sardine oil as a replacement for olive oil + anchovy in other recipes. However, that's not a swap I can find much support for online; Serious Eats even goes so far as to insist on anchovies in Pasta con le Sarde itself.

To sum up: feel free to experiment a little, but that oil is not particularly useful, and you're more likely to just throw it out.

Fish spread would be an example where you can reuse the oil, since you aim for the fishy taste anyway.

My basic approach is to mash the sardines (or any other kind of canned fish in oil) with a fork, and mix them with some cream cheese. The oil not only adds flavour, but also some additional creamyness (and I would add a dash of oil for these kinds of spreads anyway).

Then maybe add one or two diced boiled eggs (the yolk is a good emulsifyier), and season as you like (I really like tandoori masala here).

I like to mix sardine oil with milk and serve it with granola. The milk neutralizes the fish flavor and it adds an interesting color to the milk. You may want to chop in fruit or add a pinch of sugar to set the flavor of the milk also.

I don't see why this cannot be used in a similar way to fish sauce. If a recipe requires a blast of concentrated fishyness go for it. The texture may be slightly different but unlikely to be of much notice. I like your frugality. I had a similar culinary upbringing.