I think I would have a trusted friend or professional security person at the event, and if your mother begins to make a scene, have him quietly walk her out. My cousin practically had to do this at his wedding, when his fiancee's parents had a huge, screaming fight behind the scenes (in front of the bride, their daughter) right before the ceremony. My cousin walked his future father-in-law out of the room and informed him that this was no time to be acting like an idiot, and if he could not hold it together, he could not come and see his daughter married.
If you want to be a man, now is the time like no other to show your wife that you are not "torn" between herself and your mom, you are cleaving to her, your wife, the way you promised to do on your wedding day. That is what happened the day you became a husband, you turned from all others, and if your mom chooses to include herself in the definition of all others that must be turned away from, that is your MOM's problem. You are a nice, dutiful son I'm sure, but you are no longer a boy trying to please his mom. You are a man trying to protect his wife, a much more significant duty now and for the next 60 years if you are lucky.
A middle ground between wringing your hands and whining that you feel torn and marching her out under guard, is to have an advance phone call to give a word of warning with your mother that you won't tolerate any scenes. But be clear to her that no scenes will be tolerated, and that if she she acts in any way but perfectly, you will not hesitate to protect your wife. This goes for emotional bullying and grandstanding just as much as it would for physical assault.
Your wife will love you for it, your mom will probably sulk and carry on about it. Let her. It's time for her to realize your world no longer revolves around herself.
Okay this is a little tricky but when you got married you are putting your wife above your mother. you dont sleep and make love to your mother (no offense) So i would stand strong next to your wife and tell your mother flat out and say if you intend to be disrespectful towards my wife in this diffucult time i would rather you not come at all. And from what i hear you still married your wife after knowing your mother disapproves so that shows you that you love and respect your wife.
This puts you in quite the predicament! But right now it's about your wife and she is in a very emotional state and sensitive to everything.....so be patient with her. Your mom is not being fair to you or your wife. Having two married sons myself...I love my daughter-in-laws because my sons do and they make my sons happy.....your mother doesn't seem to care about how happy you are. I think it's time to have a heart-to-heart with mom and let her know that she is to be very kind that day out of respect for your wife. Explain to her that the drama gets you caught in the middle and it shouldn't be this way. Tell her you love your wife very much and she's not going anywhere so it's time for acceptance. Tell her losing your mother-in-law should show everyone how precious life is and too short for bickering. That day has got to be about your wife and maybe ask your mother for her assistance in keeping it this way. Say something like..."mom, I can't imagine if this were me so please help me to make this as good a day for my wife as possible". Moms are pretty understanding and sometimes have to be reminded of things. You've been through a lot and shouldn't have to worry about being the peace keeper and I think you need to tell your mom this. You love them both and they you....someone has to let her know that everyone's life will be easier without the negativity. She may get angry at first but then she will realize that she has to abide by what you say or she may lose you. Being an only child I think maybe your mom is having trouble letting go....which can be hard to do. But this is also when you need to let mom know you're an adult and want harmony between everyone, and want to look forward to get togethers instead of fearing what will be said. You sound like a wonderful man with a wonderful wife, mom needs to accept her and quit trying to call all the shots. She did that with her family but you have your own now and she needs to respect you and yours. I think maybe if your mom thinks you are asking her for help on this day, she will feel like she is having some input and may behave herself. I'm so sorry for all that you're enduring and hope you can work things out. This is a good time to remind your mom that life is too short for drama. I wish you and your wife all the best.