Is it permissible for the guarantor to stipulate taking half of the loan from the guaranteed in exchange for his guarantee, with the amount remaining as a debt owed by the guarantor and his commitment to repay his share to the lending party?

Jurists prohibit taking compensation for a guarantee (kafalah (definition)) because it is a contract of benevolence (irfaq), not exchange (mu'awadah). It is not permissible for the guarantor (kafil) to stipulate to the guaranteed party (makful) that he lend him a portion of the loan he intends to take, because every loan that draws a benefit is usury (riba). This loan draws a benefit for the lender and is considered a price for the guarantee, which is not permissible. The fact that the borrower repays the loan directly to the lending institution does not change the ruling of the matter.