Is it permissible to purchase goods from someone who is predominantly believed to have acquired them through illicit means, such as hacking, knowing that the purchase price will be from one's own private funds? And is it permissible to sell them afterwards seeking profit?

It is not forbidden to deal with a seller of goods whose situation is unknown, because the default is innocence, and the unknown is like the non-existent. There is no doubt in dealing with a Muslim whose situation is concealed. However, if it is highly probable that he acquires goods through deceit, theft, and aggression against people's property, then it is not permissible to deal with him, especially if you are certain of his proficiency in hacking computers and bank accounts, which would make it highly likely that he is an aggressor.