Your answer lies in the contract. Check the severability clause. And, read the entire contract in context and in complete form.
Generally, the violation of one provision of a contract does not void the entire contract. Specifically to your dispute, no one can opine without reading the contract.
See and hire a local lawyer to help you if you do not understand the contract provisions by reading them yourself.
It is unlikely that such a breach would void the non-competition provision. You should consult an attorney to get the commissions and determine whether there is a basis given the language of the agreement to void the non-competition provision based upon the breach. You might also be able to sue to rescind the provision. However, do not violate the provision without consulting an attorney and seeking a judicial determination first. It could get you in signficiant trouble.