Is it permissible to benefit from a father's money that is mixed with unlawful elements due to his selling unlicensed medications at an inflated price, and is it permissible to inherit from it?

If the medications your father sells are permissible and cause no harm, then their price is lawful, even if it violates regulations. If his wealth is mixed, the predominant view is that it is permissible for you to benefit from it, especially if the majority of his wealth is lawful. Al-Mardawi mentioned in "Al-Insaf" various opinions regarding the permissibility of eating from the wealth of someone whose earnings include unlawful elements. The madhhab (school of thought) is that it is not absolutely forbidden, but disliked, with the degree of dislikeness varying based on the scarcity or abundance of the unlawful portion.