Depends of the coral you will be added to your tank. If you going to add mostly small frags 10k will be fine temporary, Once you have good growth. Upgrade to 12k to improve your colors.
Bacteria is still deep inside of the rocks, anyway you have two hours to play with, even if you kill all of them. It will come back. it just take longer
Strontium 8ppm at nsw level.Their are product that you can dose biweekly.Also have salt that will replace it after water change. I wouldn't test for it.