I think you need to leave the relationship. You have broken the basic premise of a loving relationship whether it be poly or mono , namely trust. You are not happy in the relationship you have said as much. You find your husband controlling. Although he has been working on that . The only way your relationship is going to survive is if you are brutally honest with your husband, but of course if you are it is just as likely to dis-integrate.
I think we all have to be happy with ourselves, no matter how hard we try in a relationship if we are not happy with ourself we won't be happy with the rest.
And I know that some people here will flame me for saying this, but you have tried to leave numerous times and this is an indicator that you are ready to go. I would rather have a separated husband who is still a friend then one where it becomes a total fight after.