I discovered that I can buy cream cheese at 1/4 the price per pound, but only if I buy it as a solid 10 cm x 10 cm x 40 cm brick. Assuming I only eat 1/10th of this brick per week, is there any way I can store it so it does not go moldy in the meantime? 
Most farro enthusiasts would say that there is NO substitute for farro.  More realistically, you certainly have options.  It would help if you clarified what type of recipe you were interested in making - in the absence of that information, I would suggest you consider barley if you're making a soup and quinoa if you're making a salad.  The cooking times for both of these would differ from the cooking time for farro. 