I don't want to say they can't be mathematically modeled (in a purely theoretical sense they can), but it should be apparent by now that it's very hard to do well. I wrote a post on this particular issue a while back: https://steemit.com/writing/@blocktrades/alice-has-5-ice-cubes-bob-takes-3-how-many-ice-cubes-does-alice-have-left-for-her-afternoon-thai-iced-tea
On your second point, sure. Any change in rules can potentially cause the coin users to place more value in the coin, even removal of rules they don't like.
RE: Cryptocurrency forks: why do they happen and what happens after?