Don't know the law, but that looks like you could be playing with fire if you did decide to revise the agreement.
With your husband's health problems (bad back, chronic pot use), he could receive a disabled diagnosis, or even if he just gets laid off, he in turn could apply for alimony from you, perhaps even a few years after your divorce. Make sure you know any and all repercussions of making that change.
You don't need that hanging over your head. A nice clean break may be preferable.