Apply ED before get results? How low is too low for ED?

Zlawyered

I'm sure this has been addressed already, however I have a few questions in regards to ED that I would appreciate some feedback from.
First, Just to be clear, you can only ED for ONE school, correct?

Second, should you apply ED before you take the test?
-In other words, do you have an advantage of applying early in the ED cycle, or is it irrelevant to schools as long as it's within the deadline.

Third, how low is too low for ED? (MAIN QUESTION)
- My GPA is .2 below the medium and my LSAT is 3 below the medium. My chances right now according to 7 sage are 63%. Is that too low to use my ED on? Does any one have a good rule of thumb, in terms of percentage, when it's too low of a chance to use my ED on?