When mixing words, ο is a very common vowel to use in the middle. For example καρέκλα+ποδάρια=καρεκλοπόδαρα = chair legs, Πόδι+λουτρό=ποδόλουτρο=foot bath etc
When i was in Greece last month and was trying to buy ελαιολαδο everyone was a bit surprised and asked smth like "Do u mean λάδι?" Be ready to this :)
Maybe you pronounced it wrong? Ελαιόλαδο is a very common word, I don't see why anyone would be surprised.
You are correct. Λάδι mostly means ελαιόλαδο because in Greece it is by far the most familiar kind of edible oils.
Notice than THERE IS NO GREEK word that can be stressed in a syllable more the third one from the last one. So it could not be so, unless we separate the word to 2 parts. But it is not the case here.
Where is the accent? In written form, it is over the o, but it sounds like in "ai".
The sound is correct. The accent mark is on the ο. Listen to it again. ;)
What is the word for "olive"? Because before "The salad has olives" uses the same greek word -> Η σαλάτα εχει ελαιόλαδο