Unfortunately it is legal for an employer to dock an employee's wage. However if it states in the contract that the reason for the pay reduction is to add mandatory overtime then there may be some labor laws broken. The figures you listed actually show they want you to work more hours for less money with their new wage it is around $100 less than if you remained at $14/hr and worked 8 hours OT. You work for a shitty company and should look for employment elsewhere.

Not sure what your job is or how many employees there are but you should consider unionizing, this is one of the many reasons unions came to be.