Hi MStarr- Now is the time to focus on yourself. Sounds to me like much of your married life has been focused on your H's addiction issues. This time now is a gift, to construct a healthier happier life for yourself and your boys.
If he is failing at business, what is your financial situation and future plan? Can you support yourself and your boys if he becomes unemployed? If you can get yourself into a financial situation where you are ok with or without his financial support, it can make your decisions about the relationship much clearer.
What are your dreams and ambitions? What have you not pursued because your husband took up all your energy, or because he would have belittled your ambitions? If you could have the life you wanted 5 years from now (in this scenario, imagine your H was abducted by aliens or run over by a truck) what would that life look like?