Is what the questioner did—taking money from the Kuwait Finance House to buy an apartment through an agency that sells him oil—considered a forbidden usurious loan, and how can he rid himself of this usury if it is indeed so?

It is permissible to purchase a commodity by installments and then sell it for a lower cash price to obtain liquidity (Tawarruq). This is permissible according to the majority of scholars, provided that the buyer undertakes the selling of the commodity himself. However, if the seller undertakes this, it is called organized Tawarruq, which is prohibited. If a prohibited transaction has occurred, repentance is obligatory, and there is no harm in benefiting from the money or commodity resulting from it.