Is it permissible to take a portion of the debtor's land in exchange for the loan if he defaults on payment, and would that be considered usury, with the lender bearing the registration fees? And if permissible, should the land be valued at its current price today or at its price a year and a half ago?

The debtor must repay the debt upon ability. The principle is that the borrower should only return the equivalent of what was taken. However, there is no objection for the creditor and the debtor to agree upon a substitute for the loan at the time of repayment. It is permissible to take land equivalent to the value of the loan if both parties agree to it, provided that you do not take more land than the value of your debt on it. The valuation should be at the price of the day the land was taken, not the day the loan was granted, and without any increase. As for registration fees, they are borne by the party customarily responsible for them. It is not permissible to burden the borrower with them if custom dictates that they are on the buyer.