Why would you feel guilty for speaking the truth? I don't know what your backstory is, but if it's anything like mine, don't. If you guys fell out of love or whatever and you said things that were true about the relationship but hurt his feelings, I can understand that. But sometimes you have to be harsh to get through to people. You wouldn't have been doing either of you any favors to stay longer and dance around the real problems to protect his feelings. You stated your feelings and they are valid and deserve to be addressed. Don't apologize for that.
Yeah, my stbx is obviously mentally ill. I tried to get him into any kind of therapy when we were still together and he refused. He said he didn't need someone to tell him how fucked up he was. Okay, then! Since I left I have been encouraging him to get some real help because he has been so fixated on me it's completely unhealthy. I think he needs to be medicated, and I've offered a hundred times to help him find someone through his insurance (which I filled out the paperwork for when he started his new job way after I had left), but nope. So I guess that's another reason I don't feel guilty at all.
Im sorry you have gone through this. It truly sucks to be the person watching someone they loved ruin themselves. We were both in therapy (individual and marriage) before we moved a year ago. He was released from the military therapist twice and told he was fine. I think he is just a pro at hiding his bullshit.