Custody Of Younger Brother?

My location: Chicago
Brother’s location: Pennsylvania

Idk if this is the correct group, but I’m looking for legal advice on gaining custody of my younger brother. I’m mostly looking to see if the odds would even be worth contacting a family lawyer. This is a difficult situation for me as I’m trying to make decisions in the best interest of my brother. I moved to Chicago 2 years ago and left my brother behind (he’s 16.) Our mother has been emotionally absent and verbally/emotionally abusive for years. The last 3 years, my brother has been begging for both individual and family therapy. She has refused both.

I log everything- both written and screenshots. He sends me his messages with her. For now, I encourage him to keep asking for therapy and sending me messages. I also encourage him to record their conversations/interactions. I have my own screenshots saved from conversations with her. I’m currently no contact with her as of 8 months ago due to her behaviors. My biggest questions are: 1.) what are the odds I can fight for custody on just screenshots and my brother/own accounts? 2.) how hard is to fight with verbal/emotional abuse? and 3.) if I cannot for custody- could I petition for parenting classes or something like this? I know living in different states makes this difficult. Also, she has way more money than I do. I’ve offered him a place to come stay during summer/holidays but my mom doesn’t seem to really want to make a plan since we are not talking (which I guess is fair.)

Some other things: his father is not in the picture. My mom has sole custody, but he does pay support. I’ve been his main caretaker until I moved to Chicago. I’ve given my brother other options as well. He has a “to go” bag in case things get really bad. His friends and their families know how bad his living situation is. His grades are really bad. I considered reaching out to his school counselor, however, I’m worried they will contact my mother and tell her. We’ve also discussed contacting child services, but my brother is very concerned about that and I’m trying to keep his best interest in mind. I want him to be safe. This has been a very difficult and stressful situation for me.

Thank you for your time. All advice would be fantastic!