Others will no doubt be able to give better answers, but just to get you started, I think you’ve identified one of your key challenges:
If you rely on Proton to hide your IP, how do you hide it from them?
If your goal is to reduce the data Proton has on you, I think you might benefit from compartmentalization. There’s multiple ways to go about it, but a simple approach could be this one suggested by dngray, where you use different providers for different groups/“islands”:
Many people also group calendar and email, since these are frequently implicitly tied to your real identity based on their contents, but your case may differ. 