Is it permissible to calculate Zakat al-Fitr based on a commodity whose price is forcibly set, such as wheat, knowing that liberalizing its price would make a significant difference in the amount of Zakat?

The pricing of wheat does not affect Zakat al-Fitr. Giving it out in kind is sufficient without any problem. As for giving out its value in cash, there is a dispute, but it is not permissible to give out its value according to the current pricing because it is not the real price, and because the interest of the poor is not in this diminished value.