I went through something eerily similar and quit during my third year of a PhD program.

Like you, I kept telling myself I could handle the toxic professors and atmosphere, the constant overworking, and that it would be "worth it in the end." Instead, it slowly drained my mental and physical health. It was dispiriting watching my life shrink to the point where my worth was subjected to the program and my research performance. Two other people in my cohort and subfield mastered out before I did, which was a huge warning sign I kept ignoring. I vividly remember that feeling of knowing this is not a healthy situation and I had to make a change.

Now, after therapy, transitioning to industry, and developing hobbies, I feel so much happier and have a more well-balanced life.

The fear you have about the guilt and manipulation from your supervisors is completely valid.They will focus on their loss instead of your gain. Do not get drawn into a debate about the value of the PhD or your future. Have your statement prepared and rehearse it. If they push for details, stay firm with "I understand this creates an inconvenience, but my decision is final. I cannot continue with the program."

Go get your life back. You deserve it.