Is money earned from work considered permissible if half the price of the computer used for learning was acquired through unlawful means? And does the computer's money become permissible if half its price is given in charity?

What you did, taking people's money through hacking, is forbidden (haram (definition)), and you must repent from it. Among the conditions for repentance is returning the taken money to its owner. If that is not possible, you should spend an equivalent amount in public welfare and charities. You must hasten to do this and not merely rely on intention.

As for the computer, half of which you bought with that money, you may benefit from it in permissible ways. What you acquire from it is lawful (halal (definition)), because what is incumbent upon you is the money you took from the cardholders, not what you bought with it.