I’m not a lawyer, and don’t have all of the facts. I think there are a few of challenges you might face legally.
The first is that your mother is in her 90’s, and people in their 90’s can naturally deteriorate very quickly even with excellent care; you may have to show that she would otherwise be in good health had her care been better. The second is that you MAY (I’m not a lawyer) have to demonstrate that the home was deliberately neglecting your mother, and isn’t the result of a negligent staff who have been fired for bad behavior. Just like the police department usually can’t be sued because a couple of officers do something bad, it has to filter up to the higher-ups in the department knowing (or having good cause to have known, but ignored the warning signs) that there was a problem with those officers and ignored it. I suspect that their attorneys will try to separate the actions of their staff, from those of it’s management. Finally, if they have have access to lots of legal resources, they might be able to delay and complicate the case to the point that you/your lawyer can’t afford to continue. It also may be cheaper for them to just settle out of court and pursuing a media campaign might make that option difficult/impossible.
I’m not saying this because I think you won’t win, just to present some uneducated guesses about some of the challenges you might face.
I doubt anyone could tell you your odds of success based on the limited info we have, but I would absolutely find an attorney you trust and heed their advice about issues such as talking with the press or AARP etc. Do you have friends in the prosecutors office from your police days? Perhaps they can point you in the right direction as far as people to contact regarding civil action. I genuinely empathize with you. We’re dealing with something similar with my grandmother (who is also in her 90’s) and it’s been VERY difficult on my father. Wishing you and your family the best.