I feel you man. Making progress in this area is incredibly difficult. Without structure and support, I don't know how anyone can do it. The good news is, you can definitely get rid of the habits you want to change. Repetitions and prolongations are better than blocks because you are at least getting to the sound, but I wouldn't think of it like that if you're using as a way to control your speech. Frequency is not the issue, interruption to the way you live your life, how you feel about yourself, and how you express yourself are the issues. I would recommend speech therapy, but finding the right therapist is truly critical. Many are unqualified to deal with stuttering and don't really know what they're doing. Trust me, your stuttering is not mostly psychological and it is certainly not related to breathing. The right rhythm, intonation, and stress is however you like to speak. Acceptance is imo is the best way forward, but you can't accept your stutter and try to control it. Search for an slp who understands acceptance and how to work with you to get there.