So confused...please help!

My brother exhibits all the signs of a narcissist. He is extremely ego-maniacal, anytime I hear him speak of other people he is constantly using words such as "stupid, loser, idiot" etc and it seems very apparent that he thinks everyone is lower than him. He definitely has a God-complex and thinks himself special, smarter than all others, etc. He fits all the criteria. Our father was also either NPD, Anti-social, or psychopathic, or who knows maybe a mixture of all 3 and my brother was abused terribly by him as a child, as was my mom. I believe his wife and children are his narcissistic supply because he treats them like gold from what I can see. Msyelf and my mom were his previous NS but we are now treated like s**t by him.

Here is where I am completely confused and feel like I'm losing it! For the past few years my brother has become more and more hostile towards our mother. He has blown up at the slightest mistakes on our part, made them WAY bigger than they were, degraded us for them, threatened to cut us out of his life and then made us feel like we have had to walk on eggshells to get back in his good graces. He can do this with ease because he now has 2 beautiful children, ages 3 and 1 year old, who he can easily use a pawns with us because he knows we want to see them. When he has been like trhis to me I am more dismissive of him which means he acts slightly friendlier the next time and gradually turns on the charm and makes me believe that we are doing ok again. My mom, on the other hand, receives an onslaught of criticism. He makes it seem like we are the ones doing these things to him, and like we are at fault regardless of the situation. He does this to the point where I have apologized when I knew I was not in the wrong, just to end the drama.

My mom has been saying for years that he is trying to make her look crazy. She says he has made up stories about her to other people to make her look like she is slowly "losing it". She claims he wants to steal her money. At one point he had control of all her money because he convinced her that he would invest it for her and increase her retirement savings. He later would not give her an accounting of her money, the investments, the gains/losses etc which made her ask for her money back. He threatened her several times saying she would not get it back if she continued to be demanding with him, which of course had her walking on eggshells again. When he did give back her money, there were no gains from the investments in the 6 years that he had it, despite him bragging about his investment capabilities and the increases on investments on his own money. So my mom believes he was stealing the profit the whole time. His side of the "story" is that she is becoming more and more demanding, belligerant, etc towards him and is starting to say inappropriate things to his in-laws etc (none of which I have ever been present to hear, yet at family get-togethers I have been by her side 90% of the time). He acts like because he's her son he shouldn't have to answer to her about the money or provide documents etc to show her what went on with it.

Lately her accusations have gone as far as "I think he hid a GPS in my tire and is tracking me" to "I think he has tapped my phone and is listening to my conversations". Now I am starting to question things! I know what I have seen of his behaviour and I know my mom very well. My mom has always been kind, patient, gentle, caring, etc. My brother has always been authoritative, demanding, and talked down to or about people. Yet recently he called me, turning on the charm again, saying he was very concerned about her and can't understand why she is acting so badly towards him etc and that he is concerned she may be in early stages of Alzheimers or dementia. In thinking about this further I have seen many things from her (memory loss, misplacing things, some personality changes, overly emotional, and possibly a mini-stroke) that make me believe this is possible. I am actually thinking these things are likely a result of a mini-stroke, and she admitted to me recently that she thinks she may have recently had one and that she had one a few years ago. She has been hiding these issues from us.

In light of this, my brother insisted that we need to get her to a doctor and I agreed. He wanted us both to talk to her about it but because of her claims and the fact that I know she thinks he is trying to make her look crazy and is out to get her, I was able by some miracle to convince him that I would have this convo with her myself and get her to go. Now at first I thought he was really concerned, but without having even been to the dr yet, he is starting to say things to me like:

"She probably won't be able to drive soon and a dr will have to pull her license"
"Are you locked into a lease agreement on your apartment? Because we will probably need to get mom to sell the house and move closer to us so she will need to live with you"
"Do me a favour and find out the name of her lawyer who did her last Power of Attorney and find out who's on it"
"My wife (who's a nurse) says she will likely go downhill really fast, like less than 6 months, before she loses the ability to take care of herself independently"
"Get her referred to a doctor in our city because my wife (the nurse) can check her medical record" then adds "She has an in because she's a nurse and can make sure she's getting the best care"
"I hope you don't allow your feelings to get in the way of what's best for mom. I know you're emotional and I don't want you to argue with me over what's best for her by saying 'mom feels this' or 'mom feels that' because in the end it's not what mom feels it's what is actually best for her".

My mom is 62 and is FAR from being unable to take care of herself and be safe. I feel like I'm losing my mind because my mom insists this is another one of his ploys to make her look crazy and get her money and my brother who by all appearances is a narcissist who knows quite well how to manipulate and play with people's minds and emotions. So on one hand I feel like, yes my mom could have some early signs of dementia or effects of stroke because of behaviours etc I see with her but on the other hand my brother, who has never been diagnosed is playing like he is so concerned about her and she really is in danger for her health. I don't know who or what to believe because my mom says she's fine and he's just making her look crazy!

I have a psychology degree and I feel like I'm losing my mind trying to figure this out! On one hand I am thinking I need to make sure she is legally protected from him stealing her money if he tries (which makes so little sense to me since he makes tons of money) and on the other hand I think maybe years of abuse from my father has potentially really messed with her head. But then I realize I have also seen how my brother behaves towards both her and me and that he is a master at screwing with people's minds!

My mom already wants to change everything legally to my name (power of attorney, guardianship, will, etc) so that he can't get at her. But then I am concerned he'll just come after me! (And he has the money and legal know-how to do this) and I want no part of that. So I am wanting her to go with a public guardian and a trustee but I don't want to alarm her further (in case I AM wrong about him) by telling her the myriad of things he has recently said to me!

Please, I know this is a long and detailed read, but I really need some advice here. I absolutely want what's best for my mom. I am trying to somehow maintain a relationship with my messed up brother (who claims he has the perfect marriage with NO drama and the only drama in his life is created my my mom, and ime in the past) only because I want a relationship with my nieces. His wife is no help whatsoever because I think she's right in it all with him (possibly Narcissistic or close to it as well). I don't know if I will ever even get to have a relationship with my nieces anyways because he may just turn them against me at some point anyways. I wonder here who and what is worth saving. The money means nothing to me but it's all my mom has and it means a lot to her what happens to it etc. My mom now suspects that I am being sucked into his attempt at making her look crazy and I am being manipulated by him into believing she really is starting to lose it. But really when she lives 2 hrs away and says he's tracking her and listening to her phone calls I have a hard time believing that even knowing he is narcissitic!

Meanwhile, I am losing my mind and nobody gives a s**t. As usual I feel comepletely stuck in the middle of family drama *sigh*

Any advice???