You've identified my biggest concern. It's like you wrote this for me. I make fun of people constantly in my writing, as you know. However, I try and balance it out. I make fun of myself more than any single person. I change so many details about people and context that I don't think the people involved would know it was them. Except for my close friends but I get permission from them to write certain stories and I only write stories about my friends that have the same sense of humor as me. I don't write about their serious, personal issues. My ex husband and his mother is where it gets a little dicey. (Again I heavily hide their identities but if they or someone we know found me here - ouch.) I've consdiered deleting all the stories about them many times. But then I speak to other writers who say you are allowed to tell your story, speak your truth and why shouldn't you? I don't know. It's difficult. I wish I started out anonymously too.
I don't think you should feel guilty - you speak the truth, you don't slander people.