Renting Below Fair Market Value

The landlord is renting a home to a pastor, openly acknowledges that the amount charged is below fair market value, and reports the rental as such on their own tax return.

I find no provision in the tax code that establishes fair market value as the actual amount charged, but as "determined objectively and between unrelated parties, what it would cost to rent a comparable home (including furnishings) in a similar location." The pastor's authorized housing allowance is more than the annual rent.

Can the pastor include other allowable expenses to determine the excludable amount of his housing allowance, such as furnishings and appliances?