Mom and Son Fued--What's Going On?

Thank you so much for listening. For the purpose of this conversation, my friend's name is John.
I met John at age 15 when we moved to a small rural town, entering a new high school at 10th grade. We are both exceptionally smart (straight A students without falter). We continued to go to undergrad together, and now we are both living in the same area while he attends grad school not far from home.
Being good friends, John and I opened up about our pasts and his intrigued me. He grew up like a "model" family until his Dad left him around 9ish years old. He hates his Dad for leaving. His Mom painted his Dad as a verbal abuser and evil man. I found out through the grape vine they even lived in boxes for a month "hiding" from him, because she thought he would come for them--when in reality he had already moved to Florida. Something tells me this man is not bad at all. She grew up Catholic, became Protestant upon marriage, and now is a STRONG stereotypical hardcore Catholic Mom. His Dad and him do not communicate, but from what I hear he was relatively religious and now has his own family in Florida. John lives in Virginia. His Mom was also diagnosed with a rare disorder in the family of muscular dyst. It is not severe like MS, but it supposingly makes her tired after 4-5 hours of work.
John' Mom was always very strict, believing John should not fall victim to the world, but often, it had little to do with the world and more so: You shall be obedient and do everything I say. She really gave him no free will. She would always throw God into the mix and say things like the Bible says be obedient to your parents. I remember one time she got defensive against me when I told John that he should choose a college that best suits him. She told me I had no right to intervene and that it was a matter between John, her, and God. But in reality, it was her choice because if John were to say anything, she would pull the I am your Mom I know best. . .obey me see Bible stuff.
Well, he chose a Non-catholic protestant affiliated college and things just went downhill. His first act of choosing a choice against her will. There was nothing wrong with the college except it was not Catholic, but more importantly, not her choice.
He went off to college, we roomed together, and it did not work out. His Mom came to pick him up for Thanksgiving break and did not call beforehand like she said she would. Some random guy knocked on the door and told him his Mom was in the parking lot and seemed upset because he wasn't there. He sent me to let her know that he was on his way but quickly grabbing his stuff. Well, she tore me up in the parking lot yelling at me and telling me how her son would never meet a good Catholic girl and was going to a non-Catholic college and being influenced by my evil protestant beliefs and yada yada yada. I walked away, she sent me a five page single spaced email about how I was in the wrong for walking away, needed to respect her, and how rude it was and how it ruined Thanksgiving. She stated I needed to apologize. I sent her an email back saying I would not apologize but also that I hoped that she would realize that her son is a good guy and makes good choices. Nothing hateful, twisted, or too blunt. She retorted with how I crossed the line telling her how to raise her son (yep, still can't see how she makes that leap) and also how it was a matter between her and him and God and how I needed to learn to respect elders and yada yada yada. Needless to say, he took her side and she started painting me as manipulative and evil. She even said once that John should not room with this one guy because he was too close to me and I may have manipulated him already.
Well, we mended at the end when upon leaving I told him where to get a good deal on a textbook--he realized I did not hate him and that I acted nice despite all else.
Things with his Mom went downhill. He realized even without being close to me, that she tried to smother him with how things should go. He dated a Protestant girl, broke away from being a hardcore Catholic to more open-minded with Christianity (though still Christian), and moved out because all they did was argue. More so, she yelled at him. She always would, I forgot to mention, just yell and yell on the phone for 2-3 hours straight. She talks very fast and does not let anyone have a word in edge-wise. He says he has to go but she keeps talking. He never hangs up because he feels it is rude.
He has tried to make things work but they don't and I see him so desperately want them to. If he does not do things how she wants them, chaos ensues. For example, he participated in a play that portrayed the struggle between right and wrong and it involved a Catholic priest. She went haywire did not see it and brings it up a lot. Because he did not listen when she said no he could not do it. As a grad student, he participated in his alumni undergrad choir and she went haywire because she did not know about the decision at all. he is going to a regional theater festival because he won an award and she did not give him permission. Haywire. He came home for Christmas and like I thought, she yelled at him all day and never let go about how he was a sinner and going to burn in hell for not obeying her and yada yada yada. He left, she called and said lets try and make Christmas work, he came back, 2am on the 26th the arguing pursued. He is staying now because they are going Thursday to his Grandpa and he has cancer and so it kind of guilt-trips him into staying because he doesn't want his Grandpa knowing how bad things are. If he left, she'd throw that Grandpa has cancer and is dying card at him.
What should he do. More so, what could be some roots of problems?
I expect mental illness. Many people do, adults too. When we were in high school, his good friend invited him to their house and the Mom made a good breakfast and she went haywire on her for trying to up-seize her as a Mom because she never made Bfast. She later approached her at a school concert in private and said she talked around and it seems like this was typical of her, trying to be the best Mom.
My advice to John has been to be firm, immediate, specific, effective, and calm. Telling him to state things like, "I want a relationship, but that begins with communication and conversation. This is not a conversation because all you are doing is yelling at me. When you are ready to talk peacefully and together, then we can". Lately, I told him this is going to take a whole lot of time and I think he needs to take time and separate himself from the situation and that walking away may be best at this moment in time, because there is no healing. He goes back and she just one-sided yells. She is not ready to listen. Now, I am not sure what to tell him. Advice? He won't see a counselor and she would die before she ever went.

My advice to John has been to be firm, immediate, specific, effective, and calm. Telling him to state things like, "I want a relationship, but that begins with communication and conversation. This is not a conversation because all you are doing is yelling at me. When you are ready to talk peacefully and together, then we can". Lately, I told him this is going to take a whole lot of time and I think he needs to take time and separate himself from the situation and that walking away may be best at this moment in time, because there is no healing.

Your advice is good advice. The woman sounds crazy, a PD seems likely. Possibly Histrionic/narcissist?
You cannot have conversation/communication with a narcissist, they talk at you not to you. Any attempt to explain the problems to her will result in narc rage because she would perceive it as an insult, criticism, therefore making her angry and indignant.
He needs to get away and have minimal contact or no contact at all.
Sometimes it is impossible to have a relationship with a HNP they are so destructive.
The fact she will not see a councilor is telling, pathological Ns do not seek treatment (regardless of what you might read on here) Why not? Because they are perfect, they never admit fault, in their eyes its everyone else that needs fixing.
Never love anything that can't can't love you back.
John seems to be religious so I recommend these books, they might help try them.

Narcissistic Predicaments: A Biblical Guide To Navigating The Schemes, Snares, And No-Win Situations Unique To Abusive Families.
By Sister Renee or

Breaking the Bonds of Adult Child Abuse:
A Biblical Textbook on Abusive Narcissistic Families, How They Operate, and How to Deal With Them
By Sister Renee.