Sorry, haven't read whole thread but can I ask, would you consider yourself a perfectionist at all?
I recognise some of your OP from my first time round with toddlerhood. Sometimes my jaw would ache from smiling so much - I felt I wasn't expressing any genuine emotion because I was being "on" as fabulous mum all the time. How exhausting, and how demoralising when it doesn't work out.
IME, if you put a lot of pressure on yourself to be the perfect mum, it normally ends up as you have described above.
Try to relax and not be so hard on yourself. Try to say "so be it" if you're going to be late or she's playing up.
My mantra became (especially at bed time) well, when you're ready to come up, I'll be upstairs reading stories. And I'd just go up without her. I tried to take the confrontation out of things and the bedtime trick was particularly successful.
Just remember, she just hasn't the capacity to think in the same way as you, and most often she's just finding ways to entertain herself and if she sees she has pushed a button, she's at that age where she'll push it and push it and push it.
Easier said than done, but just try not to react. Talk your own advice and walk away. "when you're ready to do it properly, you let me know".
Go into your room and pick up a paper or something and make like you're reading it.
If she strops, ignore it until she's bored of herself and ready to comply.
All good theoretical advice. It doesn't always work out that way, but let's say 6 or 7 times out of 10 it does.
Good luck, and keep posting if you still feel like shite. We've all been there and can support you.