possessive mother in law

Ladies, I really need some advice from an unbiased group of women. 
I gave birth to my first child on February 16. I had an all natural delivery but was in labour for 20 hours total and had a second degree tear. Needles to say, I was very sore after and tired! But, I was so excited to finally meet my daughter that I didn't rest. Prior to this, my SO and I agreed we would not be having visitors for the first couple of weeks. He at first was not on board but I did a lot of research and found it to be quite normal to limit your visitors. After a long discussion, he agreed that we would spend the time together and without visitors. This is our first child and my so had two weeks off from work to spend with us. I thought for the first two weeks, it would be just us. I was so excited and wanted us to bond as a little family. Fast forward to post delivery and my daughter was born with jaundice and had a lot of trouble latching as a result. She was so tired that I couldnt even get her to feed. I was devestated. We ended up staying 4 nights in the hospital. Eventually, I had to cave and formula feed because she had lost too much weight and needed to eat. They discharged us and we were on our way home! Now, I let both my parents and my so parents visit in the hospital but asked for privacy during the first couple of weeks. My parents were on board and said to msg if we needed anything. My so parents didn't take it so well. While in visiting in the hospital, my so mother was very hyper and was handling my daughter a little rough. Trying to take her out of the room and put headbands on her. She made me so angry that I paged for a nurse just to get her to leave. Well, when we arrived home, I found out that while she was at our house to feed our cat, she moved around stuff in my daughters nursery. I was upset but didn't want it to ruin our happy moment. As soon as we got home, she was msging my so to come over. I was exhausted, needed to shower and was anxious to start pumping since my BM was not coming in. We were also on a 2 hr feeding schedule as per the hospital nurses and I had to pump as well. My so told her we needed time to get settled. The next day, my so suddenly changed his view on the no visitor rule and seemed upset with me. He was on his phone a lot and I noticed he was msging his mom. She was sending him msgs saying: a grandmother shouldn't have to beg to see her granddaughter, this seems selfish and hurtful, you know as soon as you go back to work, she will take the baby to her moms - all msgs I saw from her. Him and I had a huge argument about it and he said all of the things she said in her msgs to me (he doesn't know I saw the msgs). I couldn't believe he would call me selfish after all I went through to give him a child. I was hysterically crying as I had barely slept but I put my foot down. I was asking for two weeks, not an enternity. The arguing became unbearable so I agreed to have her come over for a half hour. I set a rule that everyone had to wash and sanitize their hands and no kissing baby (all rules the nurse told us to follow). My so said he told them ahead of time but when she got here, she refused to sanitize her hands. I had to force her.  Then, she kept kissing her when I wasn't looking. I was livid when she left and we continued to argue. My daughter is now 6 weeks old and we have the same fight weekly. His mother will not leave us alone. She has a nursery setup at her house and she thinks she is having her for sleepovers which she is not. She is a heavy smoker and she smokes in her house. My so agreed to this but he's obviously easily pursuaded by her. She sends him msgs daily asking when she can come over. She even told him not to let my baptize my daughter as she does not agree with it. She does not include me in anything and is rude and cold with me when I see here. Even his sister is acting the same way. His sister had a baby 2 weeks ago and his family is livid that I have not brought my daughter over for them to meet one another. They are babies and both need to be vaccinated. Plus, his sister lets people smoke in her house as well. 
My so and I are engaged and I was so excited to start planning my wedding but now, I don't even want to be apart of his family. His mother told him to get me checked for PPD because my behaviour is not "normal". I feel fine other than the stress she is causing me and my family. I eventually got milk in but my supply won't increase. I am still pumping and my baby is still on a 3 hr feeding schedule so I have limited time between feedings and don't want  someone here while I am pumping. She has no respect for me and my wishes but wants me to accommodate her in every way. My so seems to have my back but then changes his stance on things suddenly. I don't know how much longer I can take this. His mother is putting a huge strain on our relationship and I don't even know that we'll make it down the aisle. This was supposed to be such a happy time and now all I think about is how awful it was when I got home from the hospital. 
Does anyone have any advice? I am to the point where I want to rip her head off but I'm scared my so will be angry with me. He is a good father and normally a good partner but I don't know where he is coming from on this. 
If anyone has experienced the same thing, please let me know how you dealt with it. 
**please no negative comments, I am genuinely looking for help**