Add to your list of ingredients just a bit of mustard powder and lemon juice. Mayonnaise made the real way is the best, but it can be a PITA to make with out a good food processor.
I’ve made mayo in a regular blender. Also in a bowl with a stick blender. I have a recipe for mayo made with a combination of coconut oil and a good grade of extra-virgin olive oil.
I sometimes do. I’ve also added whey collected from the top of yogurt. It’s supposed to make it last longer.