Since the only way to reduce CH is to drain and refill (or perhaps an expensive reverse osmosis treatment), and given you're in AZ, you're not going to lower it a whole lot by draining - you don't have a target CH. You simply track it so that you can keep an eye on your CSI number - which will let you maintain your pool balance to prevent scaling (or prevent destroying your plaster). So 450 is fine - leave it alone. 
Right now, your water is likely quite cold. This means I personally wouldn't lower the pH to 7.2 - you're likely going to want to leave it higher to avoid your CSI dropping to a point where the water starts leaching calcium out of your plaster. While the normal SLAM guidelines have you lowering it to 7.2, I'd be tempted to leave it at 7.8 -please wait for an expert to weigh in on that statement. MOD note: You got it right! No need for anyone else to say anything!
The rest of your getting ready looks pretty good to me.
Right now, your water is likely quite cold. This means I personally wouldn't lower the pH to 7.2 - you're likely going to want to leave it higher to avoid your CSI dropping to a point where the water starts leaching calcium out of your plaster. While the normal SLAM guidelines have you lowering it to 7.2, I'd be tempted to leave it at 7.8 -
The rest of your getting ready looks pretty good to me.
