ProtonMail has responded to some of his questions regarding in the past.
I still don’t fully trust ProtonMail but that’s just my personal opinion. They have suspended an account of mine in the past and refused to explain why. Claimed I used the email for spam while I only sent less than 10 emails during a year period. My email shows up in some leaked copy written content by SANS institutions shortly before they blocked my account. I would bet money that was the reason.