the amount of fat used in real world pemmican is 1:1 by weight, meat:tallow. the meat is first dried, then ground, then mixed with melted fat. left to cool and harden. you can add basically whatever to that so long as it contains no water. dried fruits, and grains. though if you add grains its less pemmican and more a weird bread.
No, olive oil is only used for oil lamps and linseed oil has no use. :<
in the real world i know you can use a whole host of thing to treat hides, egg yoke, plant oil, fish oil. you name it. the actual important part of furs and hides is working them after curing so the hides stay pliable when dry. furs are still often smoked as part of the preservation process.