My response:
No, quitting would not be a "breach" since they have already breached your contract. Your remedy, first, would be to lodge a formal, written, complaint with the person with whom you made the contract - - placing them on "actual notice" of their breach, and demanding that the breach be cured.
Next, do the same thing by mail, but make sure you send it to the person by Certified Return Receipt Requested mail. Inform that person they have 5 days from the date of the letter to "cure" the breach, or you will quit.
If you're fired, then you'll have a remedy to sue for damages, based upon your contract term length. So, figure out what your term length is under the contract, and multiply that by your hourly wage.
IAAL