The Balancing Act of Homework

Enrolling Sylvia into KIPP LA Prep has solved the majority of my problems with the public education system. She's learning critical thinking skills, she's got teachers who believe that EVERY child is capable of succeeding, we have access to the teachers and staff cell phone numbers and email addresses, I have a parents website where I can access her grades, the principal has a breakfast meeting with the parents once a month, she's in school longer hours, she has P.E. and music and art as part of her curriculum, and she's doing theatre and is now an Ambassador to the school. I'm seriously in love with this school.
The one problem that hasn't gone away, and has actually gotten worse, is that of homework. She's usually doing homework until 9 pm, and the last 2 nights it's been until 10 pm. Not only do I think this is excessive and that she's not getting enough sleep, it's also cutting into my precious "me time."
I've been trying to be there for her because I know my involvement means a lot to her. I've been offering her what I felt was more moral support then academic help. I never give her the answers to any question, but I confirm when she has the right answer, or help her brainstorm ideas (again, mainly offering validation), I help her manage her time. I have her take 10-minute breaks and set the timer for her. But lately, not only is this taking up more of my time from getting laundry done or vacuuming (I know, so exciting!), she also seems to need more of my actual help in getting the work done.
Two nights ago, I worked with her on every problem of her math homework, which was finding the Least Common Multiple. There were about 20 problems, and each one probably took at least 2 minutes to solve. That's 40 minutes right there, and then there's the 20-minutes of reading, there's the page of journal writing, the vocabulary exercises, the social sciences homework, and the homework for music and/or technology and/or art.
Last night, I started to feel like she was taking advantage of me in helping her with her long division. I was trying to show her ways to break it down, since it seemed to terrify her. I was telling her to do some estimating to guide her in finding the right numbers, and leading her through the problems. A little more than halfway through, I started to get very irritated. For one thing, I was completely ignoring my other daughter (thankfully, she just went in her room and is good at being by herself, but it doesn't make me feel any less bad about it), and for another, I felt like Sylvia was leaning on me way too much and wasn't really taking in any of the information I was giving her.
I walked away, told her that she needed to do this by herself since I won't be there when she takes a test on it. I knew I'd done the right thing when she lost it, crying and whining (some day, I'll have to post a blog/poem or something on how much I despise the sound of whining). I left the room and she was yelling about how she can't do it, and I stayed out of sight for a little while. I came back in and just "stopped by" on my way to the kitchen to tell her to break it down into smaller numbers, and good luck. Then I turned on the water full blast and started the dishes.
About 2 minutes later, she said, "I did it!" I just smiled, and said, "good. I knew you could!" After I finished with the dishes, I came over and saw a couple of problems were wrong so I took her back through them, and showed her one more "trick." She only had a couple more left to do and this time, when I asked her more open-ended questions about what she was going to do, she had much more productive answers than "I don't know."
It's tricky to find that balance between helping your child, and helping your child be more independent. I think I teetered over the edge of being unhelpful by helping too much, but I found my way back!
Now, if we could just do something about the length of homework assignments...