Yes, but what other things do you believe in thats existence is inconclusive?
No. It's not as reasonable to believe in miracles as it is to disbelieve in them. It's not as reasonable to believe in ghosts as it is not to believe in them. It's not as reasonable to believe in Big Foot as it is not to believe in it.
You don't need more justification. If a position isn't justified, then it doesn't make sense to think that it's true.
Theism and atheism aren't equally valid positions.
Mmmm... well, yes and no. One, the idea of an all-powerful, all-knowing, perfectly moral entity might be contradictory in and of itself. And if Santa and the Easter Bunny existed, they'd at least be physical entities that use magic in the real world. A higher power/ God on the other hand is non-physical, and supposedly exists in another realm outside our own. Science doesn't work under the assumption that such a realm exists. In this sense, Santa is somewhat more plausible, as he is at least a physical being.