Bear in mind, though, that the altcoins will probably be flooded with GPU hashers and anybody who actually buys a GPU for the purpose of mining them will likely make less than break-even.

Also, there is no way to limit the hashing rate of a particular entity; if you were to try doing so, they'd just find some way to pretend that they are two or more people and thus circumvent the artificial limitation.

There has been at least one technical definition of dust, which you can find here: https://github.com/bitcoin/bitcoin/pull/2577. Essentially, no transaction with an output of less than 5430 satoshis will be relayed no matter what the fee is.

Day trading bitcoins will inevitably lose you money in the long run unless you are a trading professional. There are other ways to make money in the Bitcoin community, though, for instance building up trust and working as an escrow. You could also look into web development, but this would require considerable experience. You really have to be among the very best to be able to live off of your bitcoin profits.