stepmom feeling done

so I am a stepmom of 3 kids, have been for almost 8 years.

I am also a mom of 1 kid that I have with the father of my stepkids.

My stepkids have entered puberty and especially with my middle stepkid has hit puberty hard.

The bond between their mom and my partner and me is fueled very negatively from her side and it has an effect on my stepkids' life.

My partner on his side is taking my stepkid's behavior very personally and I feel is being WAAAAY to hard on him. I have a great bond with my stepkids (not approved by their mom so I feel like they want to hide it because they fear their mom's judgment) and I feel I am often caught in the middle, Trying to meddle between my partner and his kid(s).

The fact is that I feel stressed all the time because I feel like I am constantly trying to put out fires.. and every time my stepson comes back to our place it feels like his mom has been fueling more hatred in my stepson towards his dad. To which my partner responds emotionally and reactive towards my stepson.

I Truly don't know what to do. my partner does nothing with my advice and is constantly making his son feel unwanted. I obviously want my stepson to feel happy and safe as he deserves to feel at home. I keep telling my partner that he needs to be the bigger man. support his kid and be the adult, to not take his behavior personally because he's dealing with hormones and huge emotions and his mom's whispers in his ear and asif that's not enough he has a developmental delay causing him to have issues with identifying and dealing with emotions along with issues in communication. (he has sli to be exact)

I cannot stay out of this, I can't accept my partner treating his kid this way. But I also don't want to be stuck in all this drama anymore it is honestly tearing me apart. It's the drama between him and his kid and the drama between him and his ex.. and the disagreements they have through their kids because they're not communicating... it is tearing me apart because it is so similar to how I grew up.

sorry for the long post. Thank you for reading, please be kind.

@Clarissa

I agree, but neither mom nor dad are willing to do either sort of counseling with, without or for the kids. Mom denied her eldest needed therapy for ASS because she thought he sided with his dad (as far as I'm aware he's trying to stay neutral) and she didn't want him to tell his therapist bad (true) things about her. (like he's openly critical about her smoking inside the house, which she does but denies)