Can I combine a drop of Obsession and a drop of vanilla oil?

Sure! You could add scented lotion or perfume. You could also use essential oils but make sure you like the smell you're adding into your slime. I would suggest only...

Yes, but it doesn't work as well. It may also leave a thin film over all the brush and then the makeup will cake when you try to put it...

Use vanilla extract.

Yes. You just want something that will stay oily for a while and not dry out too quickly.

Yes, but that will require a lot of coconut oil, and it will alter the flavor of the tempura.

Yes, in theory, any new and non-obvious combination of existing inventions may qualify as an improvement invention on its own. You would need to do some searching on your own...

Priests can only equip Maces and Daggers as weapons. Dagger is the preferred weapon, as it is usually famed for its high dps.