So how do I keep the PH from spiking, I don't like adding an oz of dry acid every day..
I have somewhat similar water, very low CH from the tap. I don't really worry about keeping the TA at a certain level and only focus on PH. My TA is usually 30-40 and my PH hovers around 7.6-7.8. When it gets up to about 8, I put in a Tbsp on muriatic acid and that lowers it a few notches. I've found keeping it simple works best for me, just liquid chlorine and muriatic acid (and testing 2x a day). I have used MPS but that always made my PH drop like a rock and then I'd have to add baking soda to raise it again, so I stopped using it. I've only had the tub about eight months or so, so I'm still learning. But after 3 purges with Ahhsome now, it's really easy as long as you have the time to test.