Is it permissible for a friend to demand the value of gifts he gave after a dispute between them, and is that considered a debt owed by the recipient, and must the recipient pay the difference in cash?

An absolute gift cannot be revoked once it has been taken possession of. As for a gift of recompense (a gift for which the giver expects a return), it may be reclaimed as long as no recompense has been given for it, and it is subject to the rules of a sale. If the giver's intention for recompense with his gifts is proven, then their value becomes a debt owed by the recipient that must be paid. Otherwise, it is not permissible to revoke them or demand their value.