On the olive oil in mayo - Kenji over at Serious Eats explains:
"You see, extra-virgin olive oil droplets are composed of many tiny fragments, many of which are bound tightly together, preventing our taste buds from picking them up. Whip the olive oil with enough vigor by, say, using a food processor or blender, and you end up shearing those bitter-tasting fragments apart from each other. The result is a mayonnaise with a markedly bitter flavor. Not only that, but these tiny fragments actually decrease the efficacy of emulsifiers like mustard and lecithin, making your sauce more likely to break" If you want some olive oil flavor he suggests brinking the mayo together with neutral oil and then whisking in some olive oil.
