Hi. I have had similar problems with my FATHER-in law. My mother-in-law never says anything offensive or takes over when I don't want her to. I can see how you would feel resentment and anger in this situation. Your husband has had to be raised by those people your kids will call grandparents so ...give him a break in that he is trying to sort out his place...he's still their kid even though he's an adult. It's difficult sometimes to transition to being an adult with adult parents. Pray for him in that. In the meantime ask God for wisdom in how to be honest with your in laws without causing division in your family.
Your MIL needs a job. Decide beforehand what you are ok with her doing or being involved in and then invite her to do those things. Once she realizes that you aren't pushing her out of the pic she will probably gladly do what you give her to do instead of trying to push herself on what you don't want her doing. The thing about you not breastfeeding because of her...you could have locked the door...if you don't have a lock they are very inexpensive. It's easy in that situation to blame her because she's under your skin in many other situations but if you really wanted to nurse your child you could have put your foot down and locked your door.
Boundaries are not mean. They are what God has given us to define what we are willing to deal with and what we are not willing to deal with. They give us the ability to build a fence around the things we are protective of and place a gate where those who have our permission can come for a period of time. They are Godly...don't feel guilty or wrong and maybe you can convey that to your husband if his heart can hear it.
The other thing that helped me tremendously with my FIN was Phillipians 4:8 Fix your thoughts on what is true (our emotions are not always lined up with truth), and honorable (what do they do that you admire and honor?), and right, and pure, and lovely, and admirable. Think about things that are excellent and worthy of praise.
When I began to think of how kind he was to my children...of how generous he's always been to all of us...about how he traveled from Florida to Delaware every 3 months (before we moved down here) to make sure his grandkids had a relationship with him...I began to think of him in light of the above verses...and my anger and resentment subsided. Not to say that he doesn't still get my goat from time to time but it's not often nor is it major.
The book Battlefield of the Mind by Joyce Meyers helped me with this.
so..be honest in love...set good boundaries and stick to them...be strong when your husband can't...pray, pray, pray, and think of what she's done that's good.
I know you will come to the other side of this.
She paints herself as the victim in all of this although my husband and I have made our boundaries clear and she is the one who continuously steps over them. After many arguments we finally agreed to not let her keep our son anymore. 
