Spiral balance repair
I'm sorry to say that I can't quite make out what kind of balance assembly you have based on this photo. Would it be possible to see a clearer photo of the end of the balance? Can you also tell me if this is a tilt or non-tilt window?
If this is a non-tilt window, then I can at least recommend what style tool you need. See our 75-005. What you need to do is have someone hold the window up for you while you reach under and hook this tool into the hole at the end of the spiral rod. Then you just pull it down, firmly.
It's important to have someone hold the window while you do this, otherwise it'll fall on your face once it's not connected to anything.