#1 implies subsequent #2's etc. Time will tell...
What is art? A tough one to start with really, but here are some thoughts:
If Damien Hirst fixes a bathroom cabinet to the wall, it's art. If I do that, it's DIY. Similarly Tracey Emin's (in)famous bed is art, whereas mine is just where I sleep, unmade or not. The only conclusion of this is either that art is something done by an artist (but then what is an artist) or art is something on display in an art gallery. Sadly both of those definitions are circular, so no help really.
Abstract art, well this may be easier to define: "if the best experts in the world can't work out which way up it's supposed to be, then it's abstract."
The scientific method: Aristotle said that heavier things fall faster than lighter ones, everyone assumed this was the case until someone bothered to try it out. Nowadays scientists are more sceptical, but the problem with some theories is that there is no practical way of testing them, string theory being an example.
However modern science is more subtle than "it's true until proven otherwise". For starters you don't get as far as "it's true" until you've done some sort of experimental verification to show that it is at least true in certain circumstances, never mind being true generally.
Then there are laws which are really axioms, the 2nd Law of Thermodynamics being a good example. And there is also the difference between theory and theorem: theorems are in fact true, we know this because they come with definitive proofs. Theories on the other hand can rarely be proven, at most they are shown to be true within the limits of experimentation and measurement.
Finally one thing we do know to be true, because it is a theorem, is that proof and truth are separate concepts. An assertion may be true, but can also be un-provable. Therefore is it is quite incorrect to say that if you can't prove it, it cannot be true. There are so many people who have a public stage of one sort or another who need to understand this.