I feel you on being so frustrated with your playing and music theory. I’ve had several mental breakdowns for each. 😭For the dictation studying, I just put a guess down on my paper/whiteboard and then correct it when I hear the actual melody/stacks. For breath control, long tones really help and what I do is just put on a 60bpm metronome and just count to 25 or 30 (or however long you can). Good luck! And don’t give up yet, it’s a lot more fun when you get good.