Because your Ca is 0, your SI is about -2.3, which is very corrosive. If you can get Ca to 200 and salt level to 2800 and a PH of 7.9 your SI will be zero or optimum.

Actually, water temperature in an outdoor pool is fairly seasonal so it is not that difficult to keep SI in check. Also, temperature has a minor affect on SI. So using the balanced example above, you need a PH of 7.9 for a temp of 55 degrees and a PH of 7.7 for a temp of 80 degrees. As Alk or Ca rise, your optimum PH drops. Also, chlorine works better for PH < 8 so you may want to target for a PH lower than that.

It is ok to let the SI swing between +- .5 and even better to keep it +- .2. Since PH is linear with SI, this means that you can have a +- .2 swing in PH to be near optimum so it should not be too hard to keep it in check.