Email is kind of like SMS. Use it only for conversations that you wouldn't mind being broadcast to the world.

I use Proton. I don't know how much they can do to address the concerns you raise though. They have to decrypt your outbound stuff in order to relay it. The inbound stuff already arrives decryrpted from the sender's SMTP relay. And since they're a centralized service provider, there's no way they're fighting on behalf of their customers in court. 

That's just the nature of email, I think, and why using it should be avoided when possible.

In general, for Proton, or just email in general, there are some best practices I tend to follow:

- Use a custom domain, paid for in Bitcoin. 

- Pay for Proton with Bitcoin.

- Connect to Proton using a VPN or even better, via their Tor site.

- Delete all emails that aren't part of an active, ongoing conversation.

Not sure what else to do beyond that. Self-hosting just doesn't seem viable due to all the IP blocking that goes on, the need for spam filtering, ISPs blocking SMTP relay ports, etc.  

 It's not just the inbound to proton.   It's also the proton to you.  They don't let you use your own PGP key in an external client.  The private key is in their web app.  Please check the podcast

Also your criticisms of self-host are not true, we've used many providers that aren't IP blocked or spam labeled.  In fact, for the setups we do, if you're stuck in spam, we'll give you your money back, so we guarantee it.  who would guarantee that if it was not possible?