I would first be clear with myself if I wanted to make a genuine apology or if such a note was a means of getting into contact with the ex. If it is about a genuine apology I would leave out what you wrote in the OP. I would open with “I don’t want anything from you”, then I would follow with “I would like to apologize for. It was wrong of me to do have done those things. I am sorry. Be well”. Most importantly, I wouldn’t expect anything back.