I couldn't answer your poll either, as I'm comfortable with my child crying sometimes (thank goodness - he's a drama king, so spending my life trying to keep him from crying would be a fruitless effort). I also believe that both hitting and yelling are going too far.
I know I've gone too far when the look in my child's eyes tells me so or when he shuts down to me and turns away.
Definitely check out the Gentle Discipline forum. Also, try to find a way to center yourself, whether it's getting up a few minutes early to meditate or just coming up with a self-check system that you can use when you feel things getting out of control. (One thing I do now is stop, close my eyes, and breathe very deeply through my nose. It helps me to calm and it helps my son to realize that I'm reaching my breaking point). It's especially important for us single moms, IMO, to have a way to process our feelings before reacting because we don't get much time to work things out for ourselves when our children aren't there.
As for your daughter: It's
extremely important to remember that intelligence and emotional development are two completely separate things. My son is quite smart, as well (at least I think so :LOL), and I fell into the habit of expecting his emotional development to match his intelligence. It just doesn't. Expecting as much will lead you to reach your breaking point much faster.
Check your expectations. Be patient. She may be doing things that older children can do, but she's still going to act and react like a 14-month-old. She's not trying to make you crazy, she just doesn't have impulse control. Repeat that over and over to yourself.
If you're interested in reading any books, let me know and I'll be happy to give you some titles that you can probably find at your library. (Reading books that remind me of my goals in parenting and remind me what age appropriate behavior is always helps me to re-center.)
Meanwhile, if you have anyone who you can trust to care for your daughter for a short period, definitely try to get some time to yourself. If you have a stroller, too, maybe plop her in and get out for a walk. This saved my sanity countless times when ds was very small.