Nasty sister in-laws

I need some advice about how to handle my nasty future sister in-laws. I have ADD which is a type of Attention Deficient Hyper Disorder known by ADHD. It’s neurological disability which can have some nasty symptoms, like cluttering, mixing up words and sentences, not being able to connect two things we know, focus when we want to, hyper focusing on things we don’t want to, hard time sleeping, forgetfulness, impulsivity, and a slew of other symptoms. My ADD also brought an anxiety disorder and depression disorder along when I was born. The side effects for the meds to treat these disabilities/disorders can be pretty nasty too. My fiancé luckily is pretty understanding of this and does not let my disabilities define his opinion an out me. His sisters who only have met me three times have tried to manipulate him into calling of the wedding by literally listing all my ADD symptoms as reasons for me being a bad person this last weekend. I had taken time off work and tried to work around their schedule, which forced me to cancel plans with my family which had been made a year a head of time. They did not even take our schedules into account. They also switched their on what was going on while they were here but excepted us to go along with them. They did not bother to tell us until it was too late to switch my days off, causing me to miss my fiancé’s grandma’s funeral. They then would fly by the seat of their pants planning new things to do but only giving us a five minute warning. This does not work for people with ADHD in general and sets us for failure. I literally had 3 panic attacks because of their planning methods. I really did try to go with their lambing but most people can’t get ready to go just after they woke up in five minutes. They also pretend to be nice to me in order to find all my flaws/ADD symptoms and medication side effects. Then their two faced act continued on to informing my fiancé that I am a horrible person because of all my uncontrollable symptoms and accused me of asking their mom for money and of not loving him. They didn’t even try to get to know me before deciding all this crap. I only found out because my fiancé and I don’t hide stuff from each other. They used me to hurt him. This is not even the first time they have done this. Last time they were in town, they went into our bedroom, saw a pregnancy test I had forgotten to throw away and my birth control. They automatically assumed I was passive aggressively trying to say I wanted to get pregnant and tie my fiancé down. If they bothered to get to know me they would know I’m terrified of getting pregnant because any child I give birth to has a high chance of getting my ADHD gene and I don’t want my kids to have to deal with that or get treated the way I was in school. Biggest problem at the moment is that I already asked them to be bridesmaids because they are his sisters and he loves them. But they have made it clear no matter what I do they are going to try to stab me in the back and frankly I really don’t want to deal with that at my wedding. I have no clue on what to do. I know my fiancé is on my side and has threatened to cut at least the older one off but I really don’t really want to be the reason his mother does not get to have all her children again. Help I don’t know what to do. How do I get them out of my bridal party without hurting their mom and painting a bigger target on my back?