My ex has agreed to a spousal support term that is too short,

We lived together for 5 years total (less two or three weeks), we were married for 3.5 yrs. I was pregnant for 20 months, basically since May 2011 and suffered one late term terminated pregnancy and 1 miscarriage before our son was born in January 2013, 12 months prior to our separation. It was shortly before the surprise late term termination that my ex and I decided to fold my business in preparation for the pending baby.
Several times during the separation process my ex insinuated that our cohabitation was much shorter than five years. I can show mail addressed to the same address as his from the time of cohabitation.
The gardening business I had was service based to high end clients in a very affluent neighbourhood however both my ex and I now live in a small town that would not support that service.
Further to that, I had embarked upon the beginnings of a new business while married, between pregnancies, but this one (as a fine artist) would be even harder to get of the ground in a short timeframe.
The company he now solely owns was born of our marriage and he earns a high income from it.

There has been a division of assets and I was not given credit for the business. We had been income splitting during our marriage but he never made me a shareholder , although while we were married he said he was going to or had said that he did. During the separation he provided documents showing himself as the sole shareholder.
If I were to refill my taxes for those years we were income splitting I would gain a tax refund and he would have to pay significant tax plus the accounting fees etc. During the separation he said he was in the process of correcting those tax years however it is possible he has not due to the cost to him. I have been advised to wait until July to ask for full disclosure.

In recent months I asked the lawyer I'd consulted with if she felt there was some legal basis to have the separation agreement set aside. I wondered if duress would count and her response was as follows:
"in my view there is not. This is a court order, not a separation agreement. In addition, there was sufficient disclosure to make an informed decision. A significant aspect of your decision to settle at the time was the cost of litigation, which was not affordable to you, and which costs were significantly negatively impacting your overall financial situation at the end of the day. While litigation is stressful, the legal test for duress is not met here.
Regards,"
The night we settled was on the eve of a court hearing where my ex had filed for primary caregiver status as well as primary residency of our son. I was a mess and out of funds, and he controlled the income flow. The lawyer would not continue with me not having the ability to pay (I'm not sure I can prove that but it was very much implied)
I don't know what happened. I think I was advised that the cost to pursue things further was perhaps greater than the potential gain. My ex showed over 200K in gross income for 2013.
Support was put in with a scheduled review. She had said that my future was far to uncertain at the time. Support was to continue until October 2016 which was a date insisted by my lawyer as it coincided with the completion of a retraining program I was researching at the time. Otherwise, my ex was extremely hesitant to pay spousal support any longer that January 2016. You probably recall the various challenges posed by my ex that in effect have foiled that retraining plan. I am now pursuing a later start date and a longer retraining program so I can do so while maintaining equal parenting of my two year old son.
Yes, most divorces are stressful, but this one seems decidedly unfair AND due to the signing of the court order it seems I am stuck with it.
Can best interest of the child not ensure that my ex cooperate with me to get me to a place of self sufficiency?!!?
Perhaps it is a good idea for me to wait for his financial disclosure in July and at that time ask the lawyer again why I did not share in the value of the business.
The thing is, come July, I will hopefully be already enrolled and have the parenting plan I need to start retraining in September.

Thank you.
Given the seemingly common knowledge that our legal system is faulty in this way, what needs to happen to regain the integrity for justice?

I appreciate your service.