Enforcing a No Compete Clause / Unpaid Bonus

I was offered and accepted a position in which I was given a signed agreement letter that promised me a set salary and benefits package. In return, 9 days later I agreed to sign a "Covenant Not to Compete Promise". After only 3.5 months with the company, the president of the company revised a mandatory employment contract that cut my total benefits package by 27%. I either signed the agreement or he would consider my refusal to sign as a resignation. I offered to come to work the next but that I did not wish to sign the mandatory contract. The president informed me that if I did not sign the revised contract by the deadline date that I would be banished from the properties and that any work done after the deadline date would not be be paid. Do I have to honor the "No Compete Clause" since the basis for me signing such was what the company promised to pay me? The company still owed me money for my sign-on bonus, am I still entitled to receive it? Would this be a situation where I was "Constructively Discharged?