You cannot fill up the vial yet, you need to wait for future updates.
Refilling Mana can be done if you enter specific locations. For example, enter the shop with the caterpillar lady.
Yes, more animated scenes will be made.
And yes, Mofu is one guy, working on this game. He does not need other people to work on the game with him unless it's about translations, making the game available in multiple languages.
This is all I know, depending on the answers from Mofu and Lipstor in the comments.