I would leave your KH alone. Use whatever your tap water provides. Quit pulling your hair out trying to target a number on a chart. Simply ignore your PH and KH for now. Increase your bubble rate a little every couple of days. Do this when you have time to watch your fish. When you see signs of distress such as gasping at the surface, crowding into one spot, lethargy etc. return the bubble rate to the last setting. That will be your maximum CO2 level for your tank. NOW you can look at your PH. Forget trying to use a lot of gadgets and calculations when dialing in CO2. The best gauge you have for determining CO2 levels are swimming in your tank.
I have never used the Tetra brand KH test so I can't comment.
I have never used the Tetra brand KH test so I can't comment.