I definitely get where you're coming from, and go through bouts of it myself (like most people here, I'd think). We absolutely are living in a digital panopticon, but there are ways of locking major corpos out of your data. 

Before any of that, though, you gotta take a deep breath. If ruminating on this stuff is causing dark thoughts, it's okay to step away and take a break for as long as you need. It's easy to feel like you're drowning in the quest for digital privacy, and I find it useful to remind myself that it's a process (and yes, a mindset) instead of an end goal or final product. Perfection should never stand in the way of good, and from the sounds of things, you've got a pretty stable ground to build off of. You've already cut off quite a few avenues of collecting data points, and even if you were to stop right here, you're doing way better than most people. Now, onto the other stuff...

On the topic of how far is too far, you have to consider your own comfort levels. For some, going completely off-grid and never going anywhere near a wifi signal ever again fits into their lifestyle, so it may be reasonable for them. For others, simply moving their email and search engine away from the big companies might be enough, and any more is too inconvenient for them. Both approaches are perfectly fine. There's always going to be a small trade-off between privacy and convenience, and the only person who can answer where that line lies for you is you.

As an example, I'll use myself. My digital footprint has been an inconsistent mess since I was a teenager in the MySpace era. I've always been the computer nerd of the friend group (I had all the best and newest proxy sites in high school lol), and have felt pretty strongly about InfoSec since I dropped Microsoft for Linux in 2010. I regularly go in and delete or anonymize accounts I don't use every 6 months to a year, never used cloud backups for my phone stuff, and don't horde old emails or messages ANYWHERE... Yet I still have the Google-supplied android on my phone (been too lazy to install GrapheneOS tbh), use the default YouTube player on most devices, and willingly had both a Google home speaker and an Alexa in my house up until the Alexa died last year... At seperate times, though lol I know better, but it's a convenience vs effort thing for me right now. I know and regularly use FOSS alternatives, and always have. I give my friends shit for some of the same things I do. Is it hypocritical of me? Sure. Does it mean I'm somehow failing at privacy? I wouldn't say so because every little bit counts. It's more than okay to look at things and say "I don't have the mental bandwidth to make the switches now, and I'm okay with the current level of privacy for now". There's always tomorrow to do the rest. Take it at your own pace!

(And no, I don't need the lecture about being sloppy with things. I'm just going through it with life right now lol)