Thanks Full of Beans that is a useful question and observation. I suspect you already know most of the answer (-:.
Thank you
Monosaturates / saturates are better for cooking so Macademia is probably best followed by olive and avocado BUT cooking is going to destroy some of the plant compounds which protect the fruit on the tree and have in olive oil be associated with a range of benefits.
Macadamia has a better Omega 3 :6 balance, where Olive and Advocado are about 10%, but Olive oil has been more extensively trialled.
All oils are high in calories and in nature access would be restricted. So how much is ideal we dont know, but the body will survive on quite low levels of Omega 6 some say 1% calories some a 1/2% and some lower, at 9 cals to a gram of oil and 70% of that in say sunflower being Omega 6 you are looking at under a teaspoon of sunflower. People including GG Pique who wrote a book OMEGA-6 EXCESS POLYUNSATURATE FOLLY 20 years ago suggests that maybe 8 or 9 grams a day is the level at which Omega 6 starts to have a negative influence but I have not as yet found the trials.
Canola has about 20% Omega 6 and 10% Omega 3 (which are both polyunsaturates and so more heat sensitive) so is arguably not good for high temperature cooking. Also some suggest that the treatment processes may cause some damage to the oils. Cold pressed canola is starting to make an appearance.
Different people hold different views.
http://editor.nourishedmagazine.com....la-oil-healthy